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The fragile X syndrome is the most common form of inherited mental retardation in humans, caused by an expansion of the cytosine-guanine-guanine (CGG) repeat in the fragile X mental retardation 1 (FMR1) gene located on the X chromosome. Antibody tests have been developed to identify fragile X patients, based on the presence or absence of fragile mental retardation protein (FMRP) in both lymphocytes and hair roots. The objective of this study was to compare correlations of hair root and lymphocyte FMRP expression with cognitive functioning in female rural area probands carrying the full mutation. Thirty females (normal, premutation, or full mutation) were selected from Indonesian fragile X families and were tested for FMRP expression in lymphocytes and hair roots using the FMRP antibody test. Subject genotype was determined by Southern blot analysis, and IQ equivalent by Raven’s Standard Progressive Matrices. Statistical analysis was by Pearson correlation. FMRP expression in blood lymphocytes was relatively higher than that in hair roots, but hair root FMRP expression was strongly correlated with cognitive functioning in female full mutation carriers (r=0.64, p=0.015), whereas no significant correlation between lymphocyte FMRP and cognitive functioning was found (r=0.31, p= 0.281). Around 14% of subjects had a normal and 7% a borderline IQ level, while 79% had mild mental impairment. In conclusion, hair root FMRP expression may be a useful marker for identification of fragile X full mutation females.

The fragile X syndrome is the most common form of inherited mental retardation in humans, caused by an expansion of the cytosine-guanine-guanine (CGG) repeat in the fragile X mental retardation 1 (FMR1) gene located on the X chromosome. Antibody tests have been developed to identify fragile X patients, based on the presence or absence of fragile mental retardation protein (FMRP) in both lymphocytes and hair roots. The objective of this study was to compare correlations of hair root and lymphocyte FMRP expression with cognitive functioning in female rural area probands carrying the full mutation. Thirty females (normal, premutation, or full mutation) were selected from Indonesian fragile X families and were tested for FMRP expression in lymphocytes and hair roots using the FMRP antibody test. Subject genotype was determined by Southern blot analysis, and IQ equivalent by Raven’s Standard Progressive Matrices. Statistical analysis was by Pearson correlation. FMRP expression in blood lymphocytes was relatively higher than that in hair roots, but hair root FMRP expression was strongly correlated with cognitive functioning in female full mutation carriers (r=0.64, p=0.015), whereas no significant correlation between lymphocyte FMRP and cognitive functioning was found (r=0.31, p= 0.281). Around 14% of subjects had a normal and 7% a borderline IQ level, while 79% had mild mental impairment. In conclusion, hair root FMRP expression may be a useful marker for identification of fragile X full mutation females.

Intracellular inclusions play a profound role in many neurodegenerative diseases. Here, we report that HR23B and HR23A, proteins that are involved in both DNA repair and shuttling proteins to the 26S proteasome for degradation, accumulate in neuronal inclusions in brain from a mouse model for FXTAS, as well as in brain material from HD, SCA3, SCA7, FTDP-17 and PD patients. Interestingly, HR23B did not significantly accumulate in tau-positive aggregates (neurofibrillary tangles) from AD patients while ubiquitin did. The sequestration of HR23 proteins in intracellular inclusions did not cause detectable accumulation of their stable binding partner in DNA repair, XPC. Surprisingly, no reduction in repair capacity was observed in primary human fibroblasts that overexpressed GFP-polyQ, a polypeptide that induces HR23B-positive inclusions in these transfected cells. This illustrates that impairment of the ubiquitin–proteasome system (UPS) by expanded glutamine repeats, including the sequestration of HR23B, is not affecting NER.

It is still unclear why absence of the fragile X protein (FMRP) leads to mental retardation and specific behavioral problems. In neurons, the protein transports specific mRNAs towards the actively translating ribosomes near the synapses.To unravel the mechanism leading to the disorder, we performed global gene expression analysis by means of the differential display method using the fragile X mouse model. To verify differential expression, we used microarray technology and real-time PCR. Three differentially expressed cDNAs showed consistent underexpression in the fragile X knockout mouse, including a GABAA receptor subunit δ, a Rho guanine exchange factor 12 and an EST BU563433. In addition, we identified 5 genes that showed differential expression dependent on the sample of RNA analysis. We consider their differential expression as provisional. It is possible that these differentially expressed genes play an important role in the cognitive and behavioral problems observed in the fragile X syndrome.

Recessive mutations in the F-box only protein 7 gene (FBXO7) cause PARK15, a mendelian form of early-onset, levodopa-responsive parkinsonism with severe loss of nigrostriatal dopaminergic neurons. However, the function of the protein encoded by FBXO7, and the pathogenesis of PARK15 remain unknown. No animal models of this disease exist. Here, we report the generation of a vertebrate model of PARK15 in zebrafish. We first show that the zebrafish Fbxo7 homolog protein (zFbxo7) is expressed abundantly in the normal zebrafish brain. Next, we used two zFbxo7-specific morpholinos (targeting protein translation and mRNA splicing, respectively), to knock down the zFbxo7 expression. The injection of either of these zFbxo7-specific morpholinos in the fish embryos induced a marked decrease in the zFbxo7 protein expression, and a range of developmental defects. Furthermore, whole-mount in situ mRNA hybridization showed abnormal patterning and significant decrease in the number of diencephalic tyrosine hydroxylase-expressing neurons, corresponding to the human nigrostriatal or ventral tegmental dopaminergic neurons. Of note, the number of the dopamine transporter-expressing neurons was much more severely depleted, suggesting dopaminergic dysfunctions earlier and larger than those due to neuronal loss. Last, the zFbxo7 morphants displayed severe locomotor disturbances (bradykinesia), which were dramatically improved by the dopaminergic agonist apomorphine. The severity of these morphological and behavioral abnormalities correlated with the severity of zFbxo7 protein deficiency. Moreover, the effects of the co-injection of zFbxo7- and p53-specific morpholinos were similar to those obtained with zFbxo7-specific morpholinos alone, supporting further the contention that the observed phenotypes were specifically due to the knock down of zFbxo7. In conclusion, this novel vertebrate model reproduces pathologic and behavioral hallmarks of human parkinsonism (dopaminergic neuronal loss and dopamine-dependent bradykinesia), representing therefore a valid tool for investigating the mechanisms of selective dopaminergic neuronal death, and screening for modifier genes and therapeutic compounds.

Mutations in the F-box only protein 7 gene (FBXO7) cause PARK15, an autosomal recessive neurodegenerative disease presenting with severe levodopa-responsive parkinsonism and pyramidal disturbances. Understanding the PARK15 pathogenesis might thus provide clues on the mechanisms of maintenance of brain dopaminergic neurons, the same which are lost in Parkinson's disease. The protein(s) encoded by FBXO7 remain very poorly characterized. Here, we show that two protein isoforms are expressed from the FBXO7 gene in normal human cells. The isoform 1 is more abundant, particularly in primary skin fibroblasts. Both isoforms are undetectable in cell lines from the PARK15 patient of an Italian family; the isoform 1 is undetectable and the isoform 2 is severely decreased in the patients from a Dutch PARK15 family. In human cell lines and mouse primary neurons, the endogenous or over-expressed, wild type FBXO7 isoform 1 displays mostly a diffuse nuclear localization. An intact N-terminus is needed for the nuclear FBXO7 localization, as N-terminal modification by PARK15-linked missense mutation, or N-terminus tag leads to cytoplasmic mislocalization. Furthermore, the N-terminus of wild type FBXO7 (but not of mutant FBXO7) is able to confer nuclear localization to profilin (a cytoplasmic protein). Our data also suggest that overexpressed mutant FBXO7 proteins (T22M, R378G and R498X) have decreased stability compared to their wild type counterpart. In human brain, FBXO7 immunoreactivity was highest in the nuclei of neurons throughout the cerebral cortex, intermediate in the globus pallidum and the substantia nigra, and lowest in the hippocampus and cerebellum. In conclusion, the common cellular abnormality found in the PARK15 patients from the Dutch and Italian families is the depletion of the FBXO7 isoform 1, which normally localizes in the cell nucleus. The activity of FBXO7 in the nucleus appears therefore crucial for the maintenance of brain neurons and the pathogenesis of PARK15.