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In this paper, we review the legacy of Gerald (Gerry) Gottlieb in various fields related to the neural control of human movement. His studies on the myotatic (stretch) reflex and postmyotatic responses to ankle joint perturbations paved the way for current explorations of long-loop reflexes and their role in the control of movement. The dual-strategy hypothesis introduced order into a large body of literature on the triphasic muscle activation patterns seen over a variety of voluntary movements in healthy persons. The dual-strategy hypothesis continues to be important for understanding the performance of subjects with disordered motor control. The principle of linear synergy (covariance of joint torques) was an attempt to solve one of the notorious problems of motor redundancy, which remains an important topic in the field. Gerry’s attitude toward the equilibrium-point hypothesis varied between rejection and using it to explore patterns of hypothetical control variables and movement variability. The discovery of reciprocal excitation in healthy neonates fostered other studies of changes in spinal cord physiology as motor skills develop. In addition, studies of people with spasticity and the effects of treatment with intrathecal baclofen were crucial in demonstrating the possibility of unmasking voluntary movements after suppression of the hyperreflexia of spasticity. Gerry Gottlieb contributed a significant body of knowledge that formed a solid foundation from which to study a variety of neurological diseases and their treatments, and a more comprehensive and parsimonious foundation to describe the neural control of human movement.

N-terminal (Nt) acetylation is a major protein modification catalyzed by N-terminal acetyltransferases (NATs). Methionine acidic N termini, including actin, are cotranslationally Nt acetylated by NatB in all eukaryotes, but animal actins containing acidic N termini, are additionally posttranslationally Nt acetylated by NAA80. Actin Nt acetylation was found to regulate cytoskeletal dynamics and motility, thus making NAA80 a potential target for cell migration regulation. In this work, we developed potent and selective bisubstrate inhibitors for NAA80 and determined the crystal structure of NAA80 in complex with such an inhibitor, revealing that NAA80 adopts a fold similar to other NAT enzymes but with a more open substrate binding region. Furthermore, in contrast to most other NATs, the substrate specificity of NAA80 is mainly derived through interactions between the enzyme and the acidic amino acids at positions 2 and 3 of the actin substrate and not residues 1 and 2. A yeast model revealed that ectopic expression of NAA80 in a strain lacking NatB activity partially restored Nt acetylation of NatB substrates, including yeast actin. Thus, NAA80 holds intrinsic capacity to posttranslationally Nt acetylate NatB-type substrates in vivo. In sum, the presence of a dominant cotranslational NatB in all eukaryotes, the specific posttranslational actin methionine removal in animals, and finally, the unique structural features of NAA80 leave only the processed actins as in vivo substrates of NAA80. Together, this study reveals the molecular and cellular basis of NAA80 Nt acetylation and provides a scaffold for development of inhibitors for the regulation of cytoskeletal properties.

Short‐chain 3‐hydroxyacyl‐CoA dehydrogenase (SCHAD), encoded by the HADH gene, is a ubiquitously expressed mitochondrial enzyme involved in fatty acid oxidation. This protein also plays a role in insulin secretion as recessive HADH mutations cause congenital hyperinsulinism of infancy (CHI) via loss of an inhibitory interaction with glutamate dehydrogenase (GDH). Here, we present a functional evaluation of 16 SCHAD missense variants identified either in CHI patients or by high‐throughput sequencing projects in various populations. To avoid interactions with endogenously produced SCHAD protein, we assessed protein stability, subcellular localization, and GDH interaction in a SCHAD knockout HEK293 cell line constructed by CRISPR‐Cas9 methodology. We also established methods for efficient SCHAD expression and purification in E. coli, and tested enzymatic activity of the variants. Our analyses showed that rare variants of unknown significance identified in populations generally had similar properties as normal SCHAD. However, the CHI‐associated variants p.Gly34Arg, p.Ile184Phe, p.Pro258Leu, and p.Gly303Ser were unstable with low protein levels detectable when expressed in HEK293 cells. Moreover, CHI variants p.Lys136Glu, p.His170Arg, and p.Met188Val presented normal protein levels but displayed clearly impaired enzymatic activity in vitro, and their interaction with GDH appeared reduced. Our results suggest that pathogenic missense variants of SCHAD either make the protein target of a post‐translational quality control system or can impair the function of SCHAD without influencing its steady‐state protein level. We did not find any evidence that rare SCHAD missense variants observed only in the general population and not in CHI patients are functionally affected. publishedVersion

Acetylation is one of the major post-translational protein modifications in the cell, with manifold effects on the protein level as well as on the metabolome level. The acetyl group, donated by the metabolite acetyl-coenzyme A, can be co- or post-translationally attached to either the α-amino group of the N-terminus of proteins or to the ε-amino group of lysine residues. These reactions are catalyzed by various N-terminal and lysine acetyltransferases. In case of lysine acetylation, the reaction is enzymatically reversible via tightly regulated and metabolism-dependent mechanisms. The interplay between acetylation and deacetylation is crucial for many important cellular processes. In recent years, our understanding of protein acetylation has increased significantly by global proteomics analyses and in depth functional studies. This review gives a general overview of protein acetylation and the respective acetyltransferases, and focuses on the regulation of metabolic processes and physiological consequences that come along with protein acetylation.

Regulators of biotransformation are of particular interest in pharmacology and toxicology, determining in part the metabolism, disposition, and toxicity of chemicals. The nuclear receptor NR1I2 (pregnane X receptor, PXR) is a prominent xenosensor that regulates the expression of biotransformation enzymes governing elimination of many exogenous as well as endogenous compounds. Zebrafish (Danio rerio) has only one gene locus for pxr, but different genetic variants have been identified in zebrafish. However, the prevalence and significance of these variants are unknown. We hypothesize that sequence variation occurring in the Pxr gene of zebrafish may affect the action and fate of many chemicals in this species, a key model organism in various fields of research, including environmental toxicology. Here, we examine variation in Pxr sequences from four different strains of zebrafish and assess the responses of each Pxr to clotrimazole and butyl-4-aminobenzoate. The Pxr variants differed in both their ability to bind these structurally different ligands and to regulate reporter gene expression in vitro. We infer that the observed sequence variations in zebrafish Pxrs likely affect the response to putative Pxr agonists in vivo and potentially cause strain-specific biotransformation of xenobiotics in zebrafish. Thus, the choice of zebrafish strain could affect the outcome of downstream toxicological studies.

The NAA10-NAA15 complex (NatA) is an N-terminal acetyltransferase that catalyzes N-terminal acetylation of ~40% of all human proteins. N-terminal acetylation has several different roles in the cell, including altering protein stability and degradation, protein localization and protein–protein interactions. In recent years several X-linked NAA10 variants have been associated with genetic disorders. We have identified a previously undescribed NAA10 c.215T>C p.(Ile72Thr) variant in three boys from two unrelated families with a milder phenotypic spectrum in comparison to most of the previously described patients with NAA10 variants. These boys have development delay, intellectual disability, and cardiac abnormalities as overlapping phenotypes. Functional studies reveal that NAA10 Ile72Thr is destabilized, while binding to NAA15 most likely is intact. Surprisingly, the NatA activity of NAA10 Ile72Thr appears normal while its monomeric activity is decreased. This study further broadens the phenotypic spectrum associated with NAA10 deficiency, and adds to the evidence that genotype–phenotype correlations for NAA10 variants are much more complex than initially anticipated.

N-terminal acetylation is a highly abundant and important protein modification in eukaryotes catalyzed by N-terminal acetyltransferases (NATs). In humans, six different NATs have been identified (NatA-NatF), each composed of individual subunits and acetylating a distinct set of substrates. Along with most NATs, NatC acts co-translationally at the ribosome. The NatC complex consists of the catalytic subunit Naa30 and the auxiliary subunits Naa35 and Naa38, and can potentially Nt-acetylate cytoplasmic proteins when the initiator methionine is followed by a bulky hydrophobic/amphipathic residue at position 2. Here, we have identified a splice variant of human NAA30, which encodes a truncated protein named Naa30288. The splice variant was abundantly present in thyroid cancer tissues and in several different human cancer cell lines. Surprisingly, Naa30288 localized predominantly to the nucleus, as opposed to annotated Naa30 which has a cytoplasmic localization. Full-length Naa30 acetylated a classical NatC substrate peptide in vitro, whereas no significant NAT activity was detected for Naa30288. Due to the nuclear localization, we also examined acetyltransferase activity towards lysine residues. Neither full-length Naa30 nor Naa30288 displayed any lysine acetyltransferase activity. Overexpression of full-length Naa30 increased cell viability via inhibition of apoptosis. In contrast, Naa30288 did not exert an anti-apoptotic effect. In sum, we identified a novel and widely expressed Naa30 isoform with a potential non-catalytic role in the nucleus.

The functional capabilities of individuals with upper limb disabilities are assessed throughout rehabilitation and treatment regimens using functional outcome measures. For the upper limb amputee population, there are none which quantitatively take into account the quality of movement while an individual is performing tasks. In this paper, we demonstrate the use of an integrated movement analysis framework, based on motion capture and ground reaction force data, to capture quantitative information about how subjects complete a commonly used functional outcome measure, the Box and Blocks Test (BBT). In order to test the usefulness of the integrated movement analysis framework in capturing the quality of movements during task performance, a motion restriction was induced in able-bodied participants that reproduces some of the limitations imposed by conventional prosthetics. Each subject performed the BBT under normal conditions and also under the motion restriction condition. The motion capture and ground force plates captured movement that significantly differed between the two conditions, with the largest differences seen in shoulder motion, in the range of motions of head tilt and elbow flexion, and in the area of the center of pressure trajectory. These preliminary results show the feasibility of incorporating standardized, quantitative movement analysis into the assessment of function for those with an upper limb disability.

Receptor for activated C-kinase 1 (RACK1) is an intracellular scaffolding protein involved in a multitude of signalling pathways. The cytoskeleton is fundamental for intracellular cell signalling as it forms an interconnected network of regulatory proteins. Here, spectrin is a central component as it forms the actin-spectrin network that serves as docking surfaces for cellular components. The interaction between RACK1 and components of spectrin, the single spectrin repeats R16, R17 and the double spectrin repeat R1617 from the α-spectrin chain were investigated by biosensor technology and docking analysis. RACK1 associated only weakly to R16 (KD = 1.0 ± 0.5 × 10(-6) M), about 20 times stronger to R1617 (KD = 5.3 ± 0.7 × 10(-8) M) and 100 times stronger to R17 (KD = 0.9 ± 0.3 × 10(-8) M). Docking analysis showed that while R16 alone preferentially docked with its B-helix, R17 docked through its A-helix and BC loop. The double repeat and RACK1 mainly formed two different complex conformations. R1617 docked tangentially to the N/C-terminal of RACK1 or radially along a groove on the outer surface of RACK1. These configurations could account for the slight increase in entropic and the decrease in enthalpic interactions for the R1617-RACK1 interaction, compared with the interactions of RACK1 to the two single repeats. Our results suggest a mode of interaction that allows spectrin to attach to the N/C part of RACK through the inter-helical AB and BC loops and adopt a multitude of configurations in between the two limiting configurations.

Recent studies revealed the power of whole-exome sequencing to identify mutations in sporadic cases with non-syndromic intellectual disability. We now identified de novo missense variants in NAA10 in two unrelated individuals, a boy and a girl, with severe global developmental delay but without any major dysmorphism by trio whole-exome sequencing. Both de novo variants were predicted to be deleterious, and we excluded other variants in this gene. This X-linked gene encodes N-alpha-acetyltransferase 10, the catalytic subunit of the NatA complex involved in multiple cellular processes. A single hypomorphic missense variant p.(Ser37Pro) was previously associated with Ogden syndrome in eight affected males from two different families. This rare disorder is characterized by a highly recognizable phenotype, global developmental delay and results in death during infancy. In an attempt to explain the discrepant phenotype, we used in vitro N-terminal acetylation assays which suggested that the severity of the phenotype correlates with the remaining catalytic activity. The variant in the Ogden syndrome patients exhibited a lower activity than the one seen in the boy with intellectual disability, while the variant in the girl was the most severe exhibiting only residual activity in the acetylation assays used. We propose that N-terminal acetyltransferase deficiency is clinically heterogeneous with the overall catalytic activity determining the phenotypic severity. publishedVersion

Background The Box and Block Test (BBT) is a functional outcome measure that is commonly used across multiple clinical populations due to its benefits of ease and speed of implementation; reliable, objective measurement; and repetition of motion. In this study, we introduce a novel outcome measure called the targeted BBT that allows for the study of initiation, grasping, and transport of objects, and also of object release. These modifications to the existing test may increase the ecological validity of the measure while still retaining the previously stated benefits of the standard BBT. Methods 19 able-bodied subjects performed the targeted BBT and two other standard tests. Using an integrated movement analysis framework based on motion capture and ground force data, quantitative information about how subjects completed these tests were captured. Kinematic parameters at the wrist, elbow, shoulder, thorax, and head, as well as measures of postural control, were calculated and statistically compared across the three tests. Results In general, the targeted BBT required significantly higher RoM at the elbow, shoulder, thorax and head when compared to standard tests. Peak angles at these joints were also higher during performance of the targeted BBT. Peak angles and RoM values for the targeted BBT were close to those found in studies of movements of able-bodied individuals performing activities of daily living. Conclusion The targeted BBT allows analysis of repetitive movements, and may more closely model common real-world object manipulation scenarios in which a user is required to control a movement from pick-up to release.

N-terminal acetylation (Nt-acetylation) by N-terminal acetyltransferases (NATs) is one of the most common protein modifications in eukaryotes. The NatC complex represents one of three major NATs of which the substrate profile remains largely unexplored. Here, we defined the in vivo human NatC Nt-acetylome on a proteome-wide scale by combining knockdown of its catalytic subunit Naa30 with positional proteomics. We identified 46 human NatC substrates, expanding our current knowledge on the substrate repertoire of NatC which now includes proteins harboring Met-Leu, Met-Ile, Met-Phe, Met-Trp, Met-Val, Met-Met, Met-His and Met-Lys N termini. Upon Naa30 depletion the expression levels of several organellar proteins were found reduced, in particular mitochondrial proteins, some of which were found to be NatC substrates. Interestingly, knockdown of Naa30 induced the loss of mitochondrial membrane potential and fragmentation of mitochondria. In conclusion, NatC N-tacetylates a large variety of proteins and is essential for mitochondrial integrity and function.

The receptor for activated C kinase 1 (RACK1) has been shown to be overexpressed in several types of cancers such as breast, colon, melanomas, and lung. RACK1 is linked to Ras-Raf-mediated signal transduction and transformed foci formation of 3T3 cells in vitro, and since this pathway is central in papillary thyroid carcinoma (PTC) oncogenesis, we hypothesized that RACK1 could play a role in the development or maintenance of PTC. No report on RACK1 expression in thyroid tissue is available; the present study was therefore aimed at identifying possible correlation of RACK1 expression at the mRNA or protein level in normal thyroid tissue compared to PTC.We used TaqMan quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry to study the RACK1 gene and protein expression in matched tumor and nontumor samples from 59 PTC patients. The tumor samples were divided into two main categories, low-risk (group 1-3) and high-risk (group 4-6), in accordance with both histological classification and clinical appearance.RACK1 mRNA and protein levels were found highly overexpressed in tumor samples, whereas Ki-Ras mRNA was found to be relatively unchanged. B-Raf mRNA expression was low and detected only in tumor samples. Sequencing analysis detected no mutations in RACK1 or Ki-Ras, but 62.7% of the patients harbored the B-Raf single-nucleotide substitution T1799A (codon V600E). Phosphorylated extracellular signal-regulated kinase (pERK) immunohistochemistry analysis demonstrated activation of the mitogen-activated protein kinase (MAPK) pathway in tumor cells. Poorly differentiated and undifferentiated PTCs expressed significantly higher RACK1 mRNA levels than well-differentiated PTCs (p0.017).Taken together, our findings point to an important role of RACK1 protein in PTC development and progression. Our data also emphasize the importance of assessing protein expression and not only mRNA levels.

SummaryMDM2 plays a key role in modulating p53 function. The MDM2 SNP309T > G promoter polymorphism enhances Sp1 binding and has been linked to cancer risk and young age at diagnosis although with conflicting evidence. We report a second MDM2 promoter polymorphism, SNP285G > C, residing on the SNP309G allele. SNP285C occurs in Caucasians only, where 7.7% (95% CI 7.6%–7.8%) of healthy individuals carry the SNP285C/309G haplotype. In vitro analyses reveals that SNP309G enhances but SNP285C strongly reduces Sp1 promoter binding. Comparing MDM2 promoter status among different cohorts of ovarian (n = 1993) and breast (n = 1973) cancer patients versus healthy controls (n = 3646), SNP285C reduced the risk of both ovarian (OR 0.74; CI 0.58–0.94) and breast cancer (OR 0.79; CI 0.62–1.00) among SNP309G carriers.

The Naa10 (Nα acetyltransferase 10) N-terminal acetyltransferase is implicated in cancer and developmental syndromes in humans. We show that its enzymatic activity is conserved in zebrafish, and that Naa10 depletion leads to developmental abnormalities., N-terminal acetylation, catalysed by N-terminal acetyltransferases (NATs), is among the most common protein modifications in eukaryotes and involves the transfer of an acetyl group from acetyl-CoA to the α-amino group of the first amino acid. Functions of N-terminal acetylation include protein degradation and sub-cellular targeting. Recent findings in humans indicate that a dysfunctional Nα-acetyltransferase (Naa) 10, the catalytic subunit of NatA, the major NAT, is associated with lethality during infancy. In the present study, we identified the Danio rerio orthologue zebrafish Naa 10 (zNaa10). In vitro N-terminal acetylation assays revealed that zNaa10 has NAT activity with substrate specificity highly similar to that of human Naa10. Spatiotemporal expression pattern was determined by in situ hybridization, showing ubiquitous expression with especially strong staining in brain and eye. By morpholino-mediated knockdown, we demonstrated that naa10 morphants displayed increased lethality, growth retardation and developmental abnormalities like bent axis, abnormal eyes and bent tails. In conclusion, we identified the zebrafish Naa10 orthologue and revealed that it is essential for normal development and viability of zebrafish.

This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0. N-terminal acetylation (NTA) catalysed by N-terminal acetyltransferases (Nats) is among the most common protein modifications in eukaryotes, but its significance is still enigmatic. Here we characterize the plant NatA complex and reveal evolutionary conservation of NatA biochemical properties in higher eukaryotes and uncover specific and essential functions of NatA for development, biosynthetic pathways and stress responses in plants. We show that NTA decreases significantly after drought stress, and NatA abundance is rapidly downregulated by the phytohormone abscisic acid. Accordingly, transgenic downregulation of NatA induces the drought stress response and results in strikingly drought resistant plants. Thus, we propose that NTA by the NatA complex acts as a cellular surveillance mechanism during stress and that imprinting of the proteome by NatA is an important switch for the control of metabolism, development and cellular stress responses downstream of abscisic acid.

Activating Ras mutations are involved in a significant fraction of human tumors. A suppressor screen using a retroviral mouse fibroblast cDNA library was performed to identify novel factors in Ras-mediated transformation. We identified a novel potent inhibitor of Ras-mediated morphological transformation encoded by a truncated version of the receptor for activated C-kinase (RACK1). The truncated protein, designated RACK1DeltaWD1, lacked the N-terminal 49 amino acids encoding the first of the 7 WD40 repeats in RACK1. RACK1DeltaWD1 expression restored contact inhibition, stress fiber formation and reduced ERK phosphorylation in Ki-Ras transformed NIH 3T3 cells. We demonstrate that truncated RACK1 is involved in complexes consisting of wild-type RACK1 and protein kinase C isoforms alpha, betaI and delta, compromising the transduction of an activated Ras signal to the Raf-MEK-ERK pathway. The cellular localization of RACK1DeltaWD1 differed from wtRACK1, indicating that signaling complexes containing the truncated version of RACK1 are incorrectly localized. Notably, 12-O-tetradecanoyl-13-phorbol acetate (TPA) mediated intracellular translocation of RACK1-interacting PKC alpha and delta was abrogated in RACK1DeltaWD1-expressing cells. Our data support a model where RACK1 acts as a key factor in Ki-Ras-mediated morphological transformation.

The X-linked lethal Ogden syndrome was the first reported human genetic disorder associated with a mutation in an N-terminal acetyltransferase (NAT) gene. The affected males harbor an Ser37Pro (S37P) mutation in the gene encoding Naa10, the catalytic subunit of NatA, the major human NAT involved in the co-translational acetylation of proteins. Structural models and molecular dynamics simulations of the human NatA and its S37P mutant highlight differences in regions involved in catalysis and at the interface between Naa10 and the auxiliary subunit hNaa15. Biochemical data further demonstrate a reduced catalytic capacity and an impaired interaction between hNaa10 S37P and Naa15 as well as Naa50 (NatE), another interactor of the NatA complex. N-Terminal acetylome analyses revealed a decreased acetylation of a subset of NatA and NatE substrates in Ogden syndrome cells, supporting the genetic findings and our hypothesis regarding reduced Nt-acetylation of a subset of NatA/NatE-type substrates as one etiology for Ogden syndrome. Furthermore, Ogden syndrome fibroblasts display abnormal cell migration and proliferation capacity, possibly linked to a perturbed retinoblastoma pathway. N-Terminal acetylation clearly plays a role in Ogden syndrome, thus revealing the in vivo importance of N-terminal acetylation in human physiology and disease. publishedVersion

Identification of causative mutations for rare genetic diseases has for long been of interest to medical geneticists. New developments within next generation sequencing have resulted in a huge increase in discovered pathogenic mutations. This is of great importance as it is the first step in the process of understanding the underlying mechanisms of different disorders. In 2011, such a sequencing study led to the identification of a point mutation in the N-terminal acetyltransferase Naa10 as the cause of a previously undescribed lethal disorder called Ogden Syndrome [1]. The NAA10 gene was previously found to be overexpressed in different types of cancer, but its dysfunction had never before been shown to cause disease. The vast majority of proteins undergo a broad range of chemical modifications either during or after their biosynthesis. These modifications increase the diversity of expressed proteins and are often crucial for their regulation and function. Protein Nα-terminal acetylation (Nt-acetylation) represents one such major modification affecting 80-90% of all soluble human proteins [2]. The N-terminal acetyltransferases (NATs) catalyze this reaction and transfer the acetyl moiety from acetyl-coenzyme A to the Nα-group of proteins' N-termini. In humans, six NAT enzymes (NatA-NatF) exist, acetylating defined sets of substrates [3]. Naa10 constitute the catalytic subunit of the NatA complex, the major NAT acetylating 40% of all cellular proteins [2]. Ogden syndrome is an X-linked disorder characterized by severe global developmental delays, craniofacial anomalies, hypotonia, cardiac arrhythmia and eventual cardiomyopathy, resulting in mortality during infancy [1]. Our recent study highlights the molecular defects of the Naa10S37P variant causing the Ogden syndrome as well as the downstream cellular implications [4]. The mutant NatA complex displayed both an impaired peptide substrate binding and NAT activity (Figure ​(Figure1)1) and furthermore, we observed a significantly reduced NatA complex formation. Our proteomic studies demonstrated a reduced Nt-acetylation level in both B-cells and fibroblasts derived from individuals with Ogden syndrome, while female carriers and wildtype family members had unchanged Nt-acetylation levels. This is the first time a human pathological condition has been linked to altered Nt-acetylation patterns. Interestingly, we observed a reduced Nt-acetylation only for a specific subset of the proteome matching the specificity of the NatA complex, thus supporting that NatA mediated acetylation is specifically perturbed in vivo in Ogden syndrome males. Ogden syndrome cells had a reduced growth rate and were less viable when cultured dispersed and stressed, but more metabolically active when kept in a dense culture. While wildtype cells entered the G0 phase, S37P cells continued to proliferate and showed a partial loss of cell-to-cell contact inhibition. Figure 1 Effects of the NAA10 p.S37P mutation in Ogden syndrome cells Naa10 is a key player in a variety of cellular pathways [3] and markers for these were investigated in Ogden syndrome cells. S37P cells revealed an increased expression of Retinoblastoma 1 (RB1), a known negative regulator of the cell cycle. Other pathways previously linked to Naa10 function such as β-catenin, Cyclin D, TSC2/mTOR/pS6K1, MYLK and β-PIX were not perturbed in S37P cells. Several studies of female carriers of X-linked mutations have shown a skewed X-chromosome inactivation, a process occurring during early development and transmitted through subsequent mitosis favoring selection of the fit cell. In our study, all carriers of the NAA10 p.S37P mutation were skewed toward the wild-type NAA10 allele explaining why these females were healthy [4]. Naa10 is conserved from yeast to humans, and the critical role of Naa10 in normal development and disease was recently further demonstrated by NAA10 knock-down studies in Danio rerio [5]. NAA10 morphants displayed increased lethality, growth retardation and severe developmental abnormalities, and revealed that Naa10 is essential for early development and viability of zebrafish. This emphasizes the importance of a normal expression level of a functional NAT/Naa10. In addition to the Ogden syndrome, further cases involving pathogenic NAA10 mutations were recently presented. Lenz microphthalmia syndrome is caused by a splice site mutation c.471+2T>A in four affected males of the same family [6]. These presented with congenital bilateral anophthalmia, postnatal growth failure, hypotonia and skeletal anomalies. The affected males had mild to severe intellectual disability (ID) and delayed motor development. De novo NAA10 mutations in the catalytic domain of Naa10 were found in males and females with intellectual disability, arrhythmia and developmental delays [7]. The variety of clinical manifestations in the patients described so far suggest that Naa10 mutants not only cause disease through one specific mechanism, but rather have pleiotropic effects, affecting different cellular functions. Some NAA10 mutations might cause a general reduction of Nt-acetylation, and thereby cause disease due to loss of acetylation of key substrates that are important for control and regulation of physiological processes, while other mutations might cause disease due to non-catalytic effects mediated by Naa10. This highlights how further molecular and cellular studies of different NAA10 mutations are vital in order to understand how these mutations are causing various human pathologies.

Receptor for activated C-kinase 1 (RACK1) is an intracellular scaffolding protein involved in a multitude of signalling pathways. The cytoskeleton is fundamental for intracellular cell signalling as it forms an interconnected network of regulatory proteins. Here, spectrin is a central component as it forms the actin-spectrin network that serves as docking surfaces for cellular components. The interaction between RACK1 and components of spectrin, the single spectrin repeats R16, R17 and the double spectrin repeat R1617 from the α-spectrin chain were investigated by biosensor technology and docking analysis. RACK1 associated only weakly to R16 (KD = 1.0 ± 0.5 × 10(-6) M), about 20 times stronger to R1617 (KD = 5.3 ± 0.7 × 10(-8) M) and 100 times stronger to R17 (KD = 0.9 ± 0.3 × 10(-8) M). Docking analysis showed that while R16 alone preferentially docked with its B-helix, R17 docked through its A-helix and BC loop. The double repeat and RACK1 mainly formed two different complex conformations. R1617 docked tangentially to the N/C-terminal of RACK1 or radially along a groove on the outer surface of RACK1. These configurations could account for the slight increase in entropic and the decrease in enthalpic interactions for the R1617-RACK1 interaction, compared with the interactions of RACK1 to the two single repeats. Our results suggest a mode of interaction that allows spectrin to attach to the N/C part of RACK through the inter-helical AB and BC loops and adopt a multitude of configurations in between the two limiting configurations.

The delay in developmental milestones in cerebral palsy (CP) is presumed to result from a nonprogressive insult to the developing central nervous system (CNS). In CP, the site(s), type, duration, and magnitude of CNS insult(s) may never be defined, and a single focus of damage may not be revealed by standard brain imaging methods. The neurological examination (i.e., assessment of reflexes, tone, and motor coordination) generally does not define the insult with precision, nor can it predict the delays in motor skill development. The CNS damage may only be suspected from the medical history during the prenatal or perinatal period; confirmation of CNS insult may be deferred until the child misses developmental milestones in the first few months or years of life. In CP, patterns of motor incoordination and delay emerge gradually over time during development. While the original CNS injury is presumed to be a nonprogressive insult to higher motor centers (e.g., cerebral motor cortex), the damage probably causes significant modulation of functional neural connections during maturation of the brain and spinal cord. Such aberrant communication in motor pathways may be caused by, or result in, motor incoordination. In turn, repetition of uncoordinated movements may reinforce aberrant neural connections with, or at, the spinal cord. In this paper, we review neural responses to stimulation of sensory and motor systems and compare data for healthy neonates and children, and children and adults with CP. Age-related differences are identified in measured onset latencies of responses, computed central conduction delays, and relative levels of excitatory drive. Differences in muscle responses are shown among subject groups for myotatic reflex activation of agonist, antagonist, and more distant limb muscles. From these data, inferences have been made that, in CP, impairments in CNS circuitry may include descending corticospinal pathways and/or spinal reflex pathways (e.g., “reciprocal excitation”). Data from a number of investigators support the theory that changes in spinal reflex pathways are likely to play a fundamental role in the development of motor control. MRDD Research Reviews 3:175-183, 1997. © 1997 Wiley-Liss, Inc.

Background: We have previously described the essential role of the retinoid-inducible nuclear factor (RINF) during differentiation of hematopoietic cells and suggested its putative involvement in myeloid leukemia and preleukemia. Here, we have investigated whether this gene could have a deregulated expression in malignant tissues compared with their normal tissues of origin and if this potential deregulation could be associated with important clinicopathological parameters. Patients and methods: RINF messenger RNA expression was examined in biopsies from locally advanced breast tumors, metastatic malignant melanomas, and papillary thyroid carcinomas and compared with their paired or nonpaired normal reference samples. Further, the prognostic role of RINF expression was evaluated in locally advanced breast cancer. Results: RINF expression was significantly higher in all tumor forms (primary breast, and thyroid cancers and metastatic melanomas) as compared with normal control tissues (P < 0.001 for each comparison). Importantly, high levels of RINF expression correlated to a poor overall survival in breast cancer (P = 0.013). This finding was confirmed in three independent public microarray datasets (P = 0.043, n = 234; P = 0.016, n = 69; P = 0.001, n = 196) and was independent of tamoxifen therapy. Notably, high levels of RINF was strongly associated with TP53 wild-type status (P = 0.002) possibly indicating that high levels of RINF could substitute for TP53 mutations as an oncogenic mechanism during the malignant development of some cases of breast cancer. Conclusions: Our data indicate that (i) RINF overexpression is associated with the malignant phenotype in solid tumors and (ii) RINF overexpression represents an independent molecular marker for poor prognosis in breast tumors.

The stretch reflex is a spinal cord pathway between a muscle's stretch receptors and its own motor units. This reflex is thought to play an important role in normal motor function, because it is unique as a monosynaptic pathway, and because its hyperactivity is a hallmark of many motor disorders. We previously reported a difference in the stretch reflexes in healthy newborn infants and nonambulatory individuals with cerebral palsy (CP): these reflexes are characterized by responses from the stretched muscle and from the reciprocal or antagonist muscle. We proposed the existence of a functional spinal cord pathway that connects both agonist and antagonist muscles at a single joint. We hypothesized that this "reciprocal excitation" is a functional pathway of all newborn infants, which during the normal course of development of motor skills in infants is eliminated. If the CNS is damaged at birth, as in CP, the pathway of reciprocal excitation endures and is reinforced. In the current study of newborns, we recorded stretch reflex responses from all major muscle groups of the lower limb. This "irradiation of reflexes" is a normal phenomenon of the newborn CNS. This pathway becomes suppressed during normal maturation and control of coordinated limb movements.

Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.

Hoewel het mechanisme van de fasische myotatische (of ‘rek’)reflex algemeen bekend is, blijft de rol die deze reflex speelt bij het looppatroon van volwassenen speculatief. Het aanleren en ontwikkelen van motorische vaardigheden met betrekking tot de ontwikkeling van de myotatische reflex vereist verdergaande studie bij zowel gezonde als neurologisch gehandicapte kinderen.

Although the mechanism of the phasic myotatic (or "stretch") reflex is well-known, the role of this reflex in adult gait remains speculative. The acquisition and development of locomotor skills with respect to the development of the myotatic reflex require further study in both healthy and neurologically impaired children. In this article, the well-documented properties of the healthy adult's myotatic reflex are compared with recent findings of the myotatic reflex in healthy infants and children and contrasted with reflex properties in patients with cerebral palsy. These data allow us to begin to characterize the emerging features of the stretch reflex in normal and pathological early development. From these data, we can begin to speculate about the relationship between changes in stretch reflexes and the acquisition of skillful movement and gait in early childhood.

Background Relapse due to chemoresistant residual disease is a major cause of death in acute myelogenous leukemia (AML). The present study was undertaken to elucidate the molecular mechanisms of chemoresistance by comparing differential gene expression in blasts from patients with resistant relapsing AML and chemosensitive AML. Results About 20 genes were identified as preferentially expressed in blasts pooled from patients with resistant disease, as compared to chemosensitive AML blasts, based on differential gene expression screening. Half of these genes encoded proteins related to protein translation, of these a novel protein related to the ribosomal stalk protein P0. Other upregulated mRNAs coded for cytochrome C oxidase III, the transcription factors ERF-2/TIS11d, and the p75 and p52 splice variants of Lens Epithelial Derived Growth Factor (LEDGF). Analysis of blasts from single patients disclosed that LEDGF/p75 was the most consistently upregulated mRNA in resistant AML. Transfection experiments demonstrated that LEDGF/p75 and p52b antagonized daunorubicin-induced and cAMP-induced apoptosis in an AML cell line. Also HEK-293 cells were protected against daunorubicin by LEDGF/p75 and p52b, whereas LEDGF/p52 splice variants lacking exon 6 had proapoptotic effects. Interestingly, full length LEDGF/p75 protected against truncated pro-apoptotic LEDGF/p75. Conclusion Our results provide evidence for an association between the overexpression of genes encoding survival proteins like LEDGF/p75 and chemo-resistance in acute myelogenous leukemia. LEDGF/p75 has previously not been shown to protect against chemotherapy, and is a potential drug target in AML.

The purpose of this study was to determine whether use of an abdominal binder would affect oxygen uptake, trunk range of motion, and duration of the stroke phase during wheelchair propulsion. The subjects were six paraplegic wheelchair athletes with T1-T6 injuries and no abdominal muscle function. Each subject performed two trials, one while wearing the binder and one without the binder. Each trial consisted of submaximal and maximal exercise tests conducted on wheelchair rollers. Oxygen uptake was determined by open circuit spirometry while heart rate was determined by telemetry. Max VO2 values averaged 2.51 l.min-1 while average maximum heart rate values were 190 b.min-1. A 3-D video-based motion analysis system was used to obtain kinematic parameters of wheelchair propulsion. In general, 30% of the cycle time was comprised of the stroke phase, while 70% was comprised of the recovery phase across speeds. There were no statistically significant effects of the abdominal binder on any of the cardiovascular or kinematic variables at submaximal or maximal levels of exercise. Under the conditions of this laboratory investigation, it appears that an abdominal binder does not alter physiological or selected biomechanical measures in highly trained athletes.

Article abstract—We applied functional magnetic resonance imaging (FMRI) to map the somatotopic organization of the primary motor cortex using voluntary movements of the hand, arm, and foot. Eight right-handed healthy subjects performed self-paced, repetitive, flexiodextension movements of the limbs while undergoing echo-planar imaging. Four subjects performed movements of the right fingers and toes, while the remaining subjects performed movements of the right fingers and elbow joint. There was statistically significant functional activity in the left primary motor cortex in all subjects. The pattern of functional activity followed a topographic representation: finger movements resulted in signal intensity changes over the convexity of the left motor cortex, whereas toe movements produced changes either at the interhemispheric fissure or on the dorsolateral surface adjacent to the interhemispheric fissure. Elbow movements overlapped the more medial signal intensity changes observed with finger movements. Functionally active regions were confined to the cortical ribbon and followed the gyral anatomy closely. These findings indicate that FMRI is capable of generating somatotopic maps of the primary motor cortex in individual subjects.

The stretch reflex is a spinal cord pathway between a muscle's stretch receptors and its own motor units. This reflex is thought to play an important role in normal motor function, because it is unique as a monosynaptic pathway, and because its hyperactivity is a hallmark of many motor disorders. We previously reported a difference in the stretch reflexes in healthy newborn infants and nonambulatory individuals with cerebral palsy (CP): these reflexes are characterized by responses from the stretched muscle and from the reciprocal or antagonist muscle. We proposed the existence of a functional spinal cord pathway that connects both agonist and antagonist muscles at a single joint. We hypothesized that this "reciprocal excitation" is a functional pathway of all newborn infants, which during the normal course of development of motor skills in infants is eliminated. If the CNS is damaged at birth, as in CP, the pathway of reciprocal excitation endures and is reinforced. In the current study of newborns, we recorded stretch reflex responses from all major muscle groups of the lower limb. This "irradiation of reflexes" is a normal phenomenon of the newborn CNS. This pathway becomes suppressed during normal maturation and control of coordinated limb movements.

In 1980, J.W. Lance offered the following operational definition of spasticity: “Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (‘muscle tone’) with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex, as one component of the upper motor neuron syndrome” (Lance 1980) [italics added]. This has come to be the most widely used definition of this collection of clinical signs. Ten years later Lance reiterated the definition with the added remarks that ‘spasticity does not include impaired voluntary movement and an abnormal posture. These are often features of upper motoneuron lesions…” (Lance 1990).

Presented at the 16th International Charles Heidelberger Symposium on Cancer Research, Coimbra, Portugal. 26–28 September 2010 publishedVersion

The purpose of this study was to determine whether a moderate to high intensity strengthening and aerobic exercise program can improve the strength, exercise capacity, gait and balance of deconditioned male nursing home residents. Ambulatory subjects who scored 30 or less on the modified Tinetti gait and balance assessment scale, who demonstrated less than 80% of age-matched lower extremity strength on isokinetic muscle testing and who gave informed consent were enrolled. Subjects were randomized to either an exercise (n = 8) or a control (n = 6) group. All participants underwent an exercise test to determine maximal oxygen uptake (VO2max) and received quantitative gait and balance measurements. The subjects assigned to the exercise group than completed a 12-wk program of weight training for the lower extremities and stationary cycling. Both the exercise and control groups were then retested. Ten outcome variables were assessed: Tinetti mobility scores, VO2max, isokinetic-tested lower extremity strength and endurance, stride length, gait velocity, stance time, gait duration, cadence and balance. The exercise group, after completion of the program, demonstrated significant improvements in Tinetti mobility scores (P < 0.05), combined right and left quadricep muscle strength (P < 0.01), right and left lower extremity muscular endurance (P < 0.01), left stride length and gait velocity (P < 0.05), although other outcome variables changed insignificantly. The control group revealed no changes of significance with the exception of improvement of the combined right and left hamstring muscle strength (P < 0.05). Nevertheless, for those outcome variables that had improved significantly in the exercise group, the changes amounted to only a 5 to 10% increase over the baseline measurements. These findings showed that an appropriately designed high intensity exercise program can result in significant although limited improvements for clinical mobility scores, strength, muscular endurance and certain gait parameters.

The sit-to-stand motion of ten healthy subjects, 65 to 76 years old, was evaluated using kinematic, force plate, and electromyographic data to characterize the sit-to-stand motion. Kinematic data collected by video, muscle activity monitored by surface electromyography, and ground reaction forces analyzed by a piezoelectric force plate were used for analysis. Using these synchronized data, three phases of the sit-to-stand motion were identified--phase 1, weight shift; phase 2, transition; and phase 3, lift. A consistent pattern of trunk and lower extremity motion was observed, and two distinct upper extremity movement strategies were identified. The onset of muscle activity occurred in the following order: erector spinae, rectus femoris, and vastus medialis (phase 1); biceps femoris, gluteus maximus, and rectus abdominus (phase 2). This characterization of the sit-to-stand motion for a small population of healthy elderly subjects serves as a basis for identifying problems in elderly patients who demonstrate difficulty getting up from a chair.

Reply from the Authors : We appreciate the insightful comments of Drs. Foundas, Hong, Leonard, and Heilman regarding our recent paper. 1 Our response to each is as follows: We measured the distance between the center of mass of the activated region and the midline for both the finger and elbow movements. Consistent with the study by Yousry et a1., 3 the mean distance was 37.7 mm …

SUMMARY Spastic patients were instructed to make accurate, rapid ankle dorsiflexion and plantarflexion movements over different distances to a target. Ankle position and surface electromyograms (EMGs) from tibialis anterior (TA) and soleus (SOL) muscles were recorded. In 3 of 8 spastic patients tested, dorsiflexion evoked velocity-dependent activation of the antagonist (SOL) muscle which impeded the movement to the extent that the limb unintentionally reversed movement direction. We propose that this activation is reflex in origin since it (1) is tightly synchronized, (2) has a large peak amplitude, (3) occurs about 50 ms after the initiation of the movement, and (4) is velocity dependent One of the 3 patients who had reflex-induced antagonist activation in dorsiflexion also demonstrated sustained clonus during plantarflexion. This usually occurred only if the target had been overshot so that the return of the limb stretched the soleus muscle and triggered clonus We conclude that in some patients, hyperactive stretch reflexes cause movement deficits.

✓ The effects of chronic electrical stimulation of the cerebellum in patients with cerebral palsy have been studied using objective tests of joint compliance, and standardized assessments of developmental reflexes and motor skills. Of 14 patients studied prospectively for 1 to 44 months, 11 showed improvement in motor function. A double-blind test of 10 patients off and on stimulation for an average 8-week period showed no significant changes. Thus, we have no proof that the functional improvements seen with long-term stimulation are the result of cerebellar stimulation.

Tendon-jerk reflexes were tested in normal, fullterm infants aged one to four days. EMGs were recorded from gastrocnemius-soleus and tibialis anterior muscles. Reflex-like EMGs were evoked when tapping sites which should not excite the muscles from which that activity is recorded--this included the simultaneous activation of antagonistic muscles by a tendon tap. The possible mechanisms which could produce these results are discussed, as are the possible relationships between the proposed pathways and the reciprocally excitatory paths in cerebral palsy.

Measurements were made from electromyograms, evoked in human soleus and tibialis anterior muscles by tendon taps. Evidence is presented to suggest that in certain motor disorders it is possible to stimulate the stretch reflex afferents from a single muscle and elicit activity both in that muscle and its antagonist at comparable latencies and levels. Responses in both muscles occur at the short latencies of an oligosynaptic or even possibly a monosynaptic pathway. We discuss the proposition that the traditional concept of spinal reciprocal innervation as an inhibitory linking of muscle antagonists must be expanded to include both inhibitory and excitatory connections. Such reciprocal excitatory connections appear pronounced in spastic patients who have suffered perinatal injuries to the immature nervous system.

The electromyographic activity evoked by forced ankle rotation in spastic patients with cerebral palsy differs markedly from that found in normal subject or in patients with adult-onset injuries to the central nervous system. Rapid dorsiflexion can produce a strong myotatic reflex electromyogram at 30 to 50 msec in the normal adult's stretched soleus muscle, while the antagonist tibialis anterior muscle remains quiet. The same is true of spastic patients whose injury has an adult onset. In patients with cerebral palsy this early response is found in both muscle groups. The pattern of “reciprocal excitation” is in marked contrast to the reciprocal inhibition normally seen. This reflex behavior suggests a fundamental developmental error in neuronal interconnections of the spinal cord in cerebral palsy.

Hoffmann and tendon jerk reflexes were tested in human subjects at various orientations between vertical, prone and supine. The data suggest that artifacts due to movement of soft tissue may explain the current disagreement in the literature on otolithic influences on these reflexes.