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The accumulation of protein aggregates is involved in the onset of many neurodegenerative diseases. Aggrephagy is a selective type of autophagy that counteracts neurodegeneration by degrading such aggregates. In this study, we found that LC3C cooperates with lysosomal TECPR1 to promote the degradation of disease-related protein aggregates in neural stem cells. The N-terminal WD-repeat domain of TECPR1 selectively binds LC3C which decorates matured autophagosomes. The interaction of LC3C and TECPR1 promotes the recruitment of autophagosomes to lysosomes for degradation. Augmented expression of TECPR1 in neural stem cells reduces the number of protein aggregates by promoting their autophagic clearance, whereas knockdown of LC3C inhibits aggrephagy. The PH domain of TECPR1 selectively interacts with PtdIns(4)P to target TECPR1 to PtdIns(4)P containing lysosomes. Exchanging the PH against a tandem-FYVE domain targets TECPR1 ectopically to endosomes. This leads to an accumulation of LC3C autophagosomes at endosomes and prevents their delivery to lysosomes., Many neurodegenerative disorders are characterised by the accumulation of protein aggregates in neurons. Here, the authors show that the lysosomal protein TECPR1 selectively recruits mature autophagosomes via an interaction with LC3C to break down protein aggregates in neural stem cells.

International audience; Amyotrophic lateral sclerosis (ALS) is a severe and incurable neurodegenerative disease. Human motor neurons generated from induced pluripotent stem cells (iPSc) offer new perspectives for disease modeling and drug testing in ALS. In standard iPSc-derived cultures, however, the two major phenotypic alterations of ALS--degeneration of motor neuron cell bodies and axons--are often obscured by cell body clustering, extensive axon criss-crossing and presence of unwanted cell types. Here, we succeeded in isolating 100% pure and standardized human motor neurons by a novel FACS double selection based on a p75(NTR) surface epitope and an HB9::RFP lentivirus reporter. The p75(NTR)/HB9::RFP motor neurons survive and grow well without forming clusters or entangled axons, are electrically excitable, contain ALS-relevant motor neuron subtypes and form functional connections with co-cultured myotubes. Importantly, they undergo rapid and massive cell death and axon degeneration in response to mutant SOD1 astrocytes. These data demonstrate the potential of FACS-isolated human iPSc-derived motor neurons for improved disease modeling and drug testing in ALS and related motor neuron diseases.

Brachial plexus injury is frequent after traffic accident in adults or shoulder dystocia in newborns. Whereas surgery can restore arm movements, therapeutic options are missing for sensory defects. Dorsal root (DR) ganglion neurons convey sensory information to the central nervous system (CNS) through a peripheral and a central axon. Central axons severed through DR section or avulsion during brachial plexus injury inefficiently regenerate and do not reenter the spinal cord. We show that a combination of microsurgery and gene therapy circumvented the functional barrier to axonal regrowth at the peripheral and CNS interface. After cervical DR section in rats, microsurgery restored anatomical continuity through a nerve graft that laterally connected the injured DR to an intact DR. Gene transfer to cells in the nerve graft induced the local release of neurotrophin-3 (NT-3) and glial cell line–derived neurotrophic factor (GDNF) and stimulated axonal regrowth. Central DR ganglion axons efficiently regenerated and invaded appropriate areas of the spinal cord dorsal horn, leading to partial recovery of nociception and proprioception. Microsurgery created conditions for functional restoration of DR ganglion central axons, which were improved in combination with gene therapy. This combination treatment provides means to reduce disability due to somatosensory defects after brachial plexus injury.

Usher syndrome is recognized as the most frequent cause of hereditary deaf-blindness. Usher syndrome type I (USH1), the most severe form of the disease, is characterized by profound congenital sensorineural deafness, constant vestibular dysfunction, and retinitis pigmentosa of prepubertal onset. This form is genetically heterogeneous and five loci (USH1A-E) have been mapped thusfar. However, only the gene responsible for USH1 B (which accounts for approximately 75% of USH1 cases) has been characterized. It encodes a long-tailed unconventional myosin, myosin VIIA, with a predicted 2215 amino acid sequence. Primers covering the complete myosin VIIA coding sequence as well as the 3' non coding sequence were designed, allowing direct sequence analysis of each of the 48 coding exons and flanking splice sites in seven patients affected by USH1. Four novel mutations were thereby identified. The possibility should now be considered of a sequence-based prenatal diagnosis in some of the families affected by this very severe form of Usher syndrome.

Two forms of inherited childhood nonsyndromic deafness (DFNB1 and DFNA3) and a Duchenne-like form of progressive muscular dystrophy (LGMD2C) have been mapped to the pericentromeric region of chromosome 13. To clone the genes responsible for these diseases we constructed a yeast artificial chromosome (YAC) contig spanning an 8-cM region between the polymorphic markers D13S175 and D13S221. The contig comprises 24 sequence-tagged sites, among which 15 were newly obtained. This contig allowed us to order the polymorphic markers centromere-D13S175-D13S141-D13S143-D13S115-AFM128yc1-D13S292-D13S283-AFM323vh5-D13S221-telomere. Eight expressed sequence tags, previously assigned to 13q11-q12 (D13S182E, D13S183E, D13S502E, D13S504E, D13S505E, D13S837E, TUBA2, ATP1AL1), were localized on the YAC contig. YAC screening of a cDNA library derived from mouse cochlea allowed us to identify an α-tubulin gene (TUBA2) that was subsequently precisely mapped within the candidate region.

Le syndrome de Usher associe une surdite congenitale et une retinite pigmentaire evolutive. Il comprend trois formes cliniques qui se transmettent toutes selon le mode autosomique recessif. Le type I designe la forme la plus grave; au moins quatre genes distincts en sont responsables. Nous avons recemment identifie le gene responsable du type IB. Ce gene code pour une myosine non conventionnelle, la myosine VIIA.

Non-syndromic, recessively inherited deafness is the most predominant form of severe inherited childhood deafness. Until now, no gene responsible for this type of deafness has been localized, due to extreme genetic heterogeneity and limited clinical differentiation. Linkage analyses using highly polymorphic microsatellite markers were performed on two consanguineous families from Tunisia affected by this form of deafness. The deafness was profound, fully penetrant and prelingual. A maximum two-point lod score of 9.88 (theta = 0.001) was found with a marker detecting a 13q locus (D13S175). Linkage was also observed to the pericentromeric 13q12 loci D13S115 and D13S143. These data map this neurosensory deafness gene to the same region of chromosome 13q as the gene for severe, childhood autosomal recessive muscular dystrophy.

International audience; By providing access to affected neurons, human induced pluripotent stem cells (iPSc) offer a unique opportunity to model human neurodegenerative diseases. We generated human iPSc from the skin fibroblasts of children with mucopolysaccharidosis type IIIB. In this fatal lysosomal storage disease, defective α-N-acetylglucosaminidase interrupts the degradation of heparan sulfate (HS) proteoglycans and induces cell disorders predominating in the central nervous system, causing relentless progression toward severe mental retardation. Partially digested proteoglycans, which affect fibroblast growth factor signaling, accumulated in patient cells. They impaired isolation of emerging iPSc unless exogenous supply of the missing enzyme cleared storage and restored cell proliferation. After several passages, patient iPSc starved of an exogenous enzyme continued to proliferate in the presence of fibroblast growth factor despite HS accumulation. Survival and neural differentiation of patient iPSc were comparable with unaffected controls. Whereas cell pathology was modest in floating neurosphere cultures, undifferentiated patient iPSc and their neuronal progeny expressed cell disorders consisting of storage vesicles and severe disorganization of Golgi ribbons associated with modified expression of the Golgi matrix protein GM130. Gene expression profiling in neural stem cells pointed to alterations of extracellular matrix constituents and cell-matrix interactions, whereas genes associated with lysosome or Golgi apparatus functions were downregulated. Taken together, these results suggest defective responses of patient undifferentiated stem cells and neurons to environmental cues, which possibly affect Golgi organization, cell migration and neuritogenesis. This could have potential consequences on post-natal neurological development, once HS proteoglycan accumulation becomes prominent in the affected child brain.

Kallmann syndrome represents the association of hypogonadotropic hypogonadism with anosmia. Three modes of transmission, X chromosome-linked, autosomal recessive and autosomal dominant, have been described. The KAL gene, responsible for the X-linked form of the disease, has been isolated and its intron-exon organization recently determined. We have searched for mutations of the KAL gene in 21 unrelated males affected by familial Kallmann syndrome. In these families, segregation of the disease was suggestive of the X-linked mode of transmission. In 2 families, large Xp22.3 deletions, both including the entire KAL gene, have been detected by Southern blot analysis. Here we report the sequence analysis of the entire coding region of the KAL gene in the 19 remaining patients. The approach consisted of sequencing each of the 14 coding exons and splice site junctions. Each exon was amplified by PCR on the genomic DNA, using oligonucleotides from the flanking intronic sequences as specific primers. Nine point mutations were identified at separate locations in four exons and one splice site, providing strong evidence for heterogeneity in mutations responsible for the X-linked Kallmann syndrome. In addition, the high frequency of unilateral renal aplasia in X-linked Kallmann patients (6 out of 11 males with identified alterations of the KAL gene) should be emphasized.

Hereditary non-syndromic profound deafness affects about 1 in 2000 children prior to language acquisition. In 80% of the cases, the mode of transmission is autosomal recessive. The number of genes involved in these recessive forms of isolated deafness (DFNB genes) has been estimated to between 30 and 100. So far, ten DFNB genes have been mapped to human chromosomes, one of which has been isolated2. By linkage analysis of a single family whose members were affected with profound deafness, some of them presenting with vestibular dysfunction, DFNB2 has been mapped to chromosome 11q13 (ref. 3). The gene responsible for a form of Usher syndrome type I, USH1B, has been assigned to the same chromosomal region4. Usher syndrome associates profound congenital deafness and vestibular dysfunction with retinitis pigmentosa. In the homologous murine region are located the shaker-1 mutations responsible for deafness and vestibular dysfunction. It has been demonstrated that the murine shaker-1 and human USH1B phenotypes result from mutations in the gene encoding myosin-VIIA5,6. Based on mapping data as well as on the similarities between the phenotypes of DFNB2-affected patients and shaker-1 mouse mutants, we have proposed that a defective myosin-VIIA may also be responsible for DFNB2 (ref. 1). Sequence analysis of each of the coding exons of the myosin-VIIA gene (MYO7A) was thus undertaken in the DFNB2-affected family. In the last nucleotide of exon 15, a G to A transition was detected, a type of mutation that is known to decrease the efficiency of splicing7‐14. Accordingly, this result shows that different mutations in MYO7A result in either an isolated or a syndromic form of deafness.

Usher syndrome type 1 (USH1) is an autosomal recessive sensory defect involving congenital profound sensorineural deafness, vestibular dysfunction and blindness (due to progressive retinitis pigmentosa)1. Six different USH1 loci have been reported. So far, only MYO7A (USH1B), encoding myosin VIIA (ref. 2), has been identified as a gene whose mutation causes the disease. Here, we report a gene underlying USH1C (MIM 276904), a USH1 subtype described in a population of Acadian descendants from Louisiana3 and in a Lebanese family4. We identified this gene (USH1C), encoding a PDZ-domain–containing protein, harmonin, in a subtracted mouse cDNA library derived from inner ear sensory areas. In patients we found a splice-site mutation, a frameshift mutation and the expansion of an intronic variable number of tandem repeat (VNTR). We showed that, in the mouse inner ear, only the sensory hair cells express harmonin. The inner ear Ush1c transcripts predicted several harmonin isoforms, some containing an additional coiled-coil domain and a proline- and serine-rich region. As several of these transcripts were absent from the eye, we propose that USH1C also underlies the DFNB18 form of isolated deafness.

International audience; The gene encoding human myosin VIIA is responsible for Usher syndrome type III (USH1B), a disease which associates profound congenital sensorineural deafness, vestibular dysfunction, and retinitis pigmentosa. The reconstituted cDNA sequence presented here predicts a 2215 amino acid protein with a typical unconventional myosin structure. This protein is expected to dimerize into a two-headed molecule. The C terminus of its tail shares homology with the membrane-binding domain of the band 4.1 protein superfamily. The gene consists of 48 coding exons. It encodes several alternatively spliced forms. In situ hybridization analysis in human embryos demonstrates that the myosin VIIA gene is expressed in the pigment epithelium and the photoreceptor cells of the retina, thus indicating that both cell types may be involved in the USH1B retinal degenerative process. In addition, the gene is expressed in the human embryonic cochlear and vestibular neuroepithelia. We suggest that deafness and vestibular dysfunction in USH1B patients result from a defect in the morphogenesis of the inner ear sensory cell stereocilia.

International audience; The gene for the X-linked Kallmann syndrome (KAL), a developmental disorder characterized by hypogonadotropic hypogonadism and anosmia, maps to Xp22.3 and has a homologous locus, KALP, on Yq11. We show here that KAL consists of 14 exons spanning 120-200 kilobases that correlate with the distribution of domains in the predicted protein including four fibronectin type III repeats. The KALP locus reveals several large deletions and a number of small insertions, deletions and base substitutions which indicate it is a non-processed pseudogene. The sequence divergence between KAL and KALP in humans, and the chromosomal location of KAL homologous sequences in other primates, suggest that KALP and the steroid sulphatase pseudogene on Yq11 were involved in the same rearrangement event on the Y chromosome during primate evolution.

Kallmann syndrome represents the association of hypogonadotropic hypogonadism with anosmia. This syndrome is from a defect in the embryonic migratory pathway of gonadotropin-releasing hormone synthesizing neurons and olfactory axons. A candidate gene for the X chromosome-linked form of the syndrome was recently isolated by using a positional cloning strategy based on deletion mapping in the Xp22.3 region. With the PCR, two exons of this candidate gene were amplified on the genomic DNAs from 18 unrelated patients affected with the X chromosome-linked Kallmann syndrome. Three different base transitions--all leading to a stop codon--and one single-base deletion responsible for a frameshift were identified. We thus conclude that the candidate gene is the actual KAL gene responsible for the X chromosome-linked Kallmann syndrome. Furthermore, unilateral renal aplasia in two unrelated patients carrying a stop mutation indicates that the KAL gene is itself responsible for this Kallmann syndrome-associated anomaly. The gene is, therefore, also involved in kidney organogenesis. Additional neurologic symptoms in Kallmann patients are also discussed.

USHER syndrome represents the association of a hearing impairment with retinitis pigmentosa1 and is the most frequent cause of deaf–blindness in humans. It is inherited as an autosomal recessive trait which is clinically and genetically heterogeneous2,3. Some patients show abnormal organization of microtubules in the axoneme of their photoreceptors cells (connecting cilium)4–6, nasal ciliar cells7 and sperm cells5, as well as widespread degeneration of the organ of Corti8. Usher syndrome type 1 (USH1) is characterized by a profound congenital sensorineural hearing loss, constant vestibular dysfunction and prepubertal onset of retinitis pigmentosa. Of three different genes responsible for USH19–11,USH1B maps to 11q13.5 (ref. 10) and accounts for about 75% of USH1 patients2,3. The mouse deafness shaker-1 (shl) mutation has been localized to the homologous murine region12,13. Taking into account the cytoskeletal abnormalities in USH patients, the identification of a gene encoding an unconventional myosin as a candidate for shaker-1(ref. 14) led us to consider the human homo-logue as a good candidate for the gene that is defective in USH1B. Here we present evidence that a gene encoding myosin VIIA is responsible for USH1B. Two different premature stop codons, a six-base-pair deletion and two different missense mutations were detected in five unrelated families. In one of these families, the mutations were identified in both alleles. These mutations, which are located at the amino-terminal end of the motor domain of the protein, are likely to result in the absence of a functional protein. Thus USH IB appears as a primary cytoskeletal protein defect. These results implicate the genes encoding other unconventional myosins and their interacting proteins as candidates for other genetic forms of Usher syndrome.

Townes-Brocks syndrome (TBS) is an autosomal dominant developmental disorder characterized by anal and thumb malformations and by ear anomalies that can affect the three compartments and usually lead to hearing loss. The gene underlying TBS, SALL1, is a human homolog of the Drosophila spalt gene which encodes a transcription factor. A search for SALL1 mutations undertaken in 11 unrelated affected individuals (five familial and six sporadic cases) led to the detection of mutations in nine of them. One nonsense and six different novel frameshift mutations, all located in the second exon, were identified. Together with the previously reported mutations [Kohlhase et al., 1999], they establish that TBS results from haploinsufficiency. The finding of de novo mutations in the sporadic cases is consistent with the proposed complete penetrance of the disease. Moreover, the occurrence of the same 826C>T transition in a CG dimer, in three sporadic cases from the present series and three sporadic cases from the other series [Kohlhase et al., 1999] (i.e., six of the eight mutations identified in sporadic cases), reveals the existence of a mutation hotspot. Six different SALL1 polymorphisms were identified in the course of the present study, three of which are clustered in a particular region of the gene that encodes a stretch of serine residues. Finally, the chromosome 16 breakpoint of a t(5;16)(p15.3;q12.1) translocation carried by a TBS-affected individual was mapped at least 180 kb telomeric to SALL1, thus indicating that a position effect underlies the disease in this individual.