@article {738, title = {Deficiencies in vesicular transport mediated by TRAPPC4 are associated with severe syndromic intellectual disability.}, journal = {Brain}, volume = {143}, year = {2020}, month = {2020 01 01}, pages = {112-130}, abstract = {

The conserved transport protein particle (TRAPP) complexes regulate key trafficking events and are required for autophagy. TRAPPC4, like its yeast Trs23 orthologue, is a core component of the TRAPP complexes and one of the essential subunits for guanine nucleotide exchange factor activity for Rab1 GTPase. Pathogenic variants in specific TRAPP subunits are associated with neurological disorders. We undertook exome sequencing in three unrelated families of Caucasian, Turkish and French-Canadian ethnicities with seven affected children that showed features of early-onset seizures, developmental delay, microcephaly, sensorineural deafness, spastic quadriparesis and progressive cortical and cerebellar atrophy in an effort to determine the genetic aetiology underlying neurodevelopmental disorders. All seven affected subjects shared the same identical rare, homozygous, potentially pathogenic variant in a non-canonical, well-conserved splice site within TRAPPC4 (hg19:chr11:g.118890966A>G; TRAPPC4: NM_016146.5; c.454+3A>G). Single nucleotide polymorphism array analysis revealed there was no haplotype shared between the tested Turkish and Caucasian families suggestive of a variant hotspot region rather than a founder effect. In silico analysis predicted the variant to cause aberrant splicing. Consistent with this, experimental evidence showed both a reduction in full-length transcript levels and an increase in levels of a shorter transcript missing exon 3, suggestive of an incompletely penetrant splice defect. TRAPPC4 protein levels were significantly reduced whilst levels of other TRAPP complex subunits remained unaffected. Native polyacrylamide gel electrophoresis and size exclusion chromatography demonstrated a defect in TRAPP complex assembly and/or stability. Intracellular trafficking through the Golgi using the marker protein VSVG-GFP-ts045 demonstrated significantly delayed entry into and exit from the Golgi in fibroblasts derived from one of the affected subjects. Lentiviral expression of wild-type TRAPPC4 in these fibroblasts restored trafficking, suggesting that the trafficking defect was due to reduced TRAPPC4 levels. Consistent with the recent association of the TRAPP complex with autophagy, we found that the fibroblasts had a basal autophagy defect and a delay in autophagic flux, possibly due to unsealed autophagosomes. These results were validated using a yeast trs23 temperature sensitive variant that exhibits constitutive and stress-induced autophagic defects at permissive temperature and a secretory defect at restrictive temperature. In summary we provide strong evidence for pathogenicity of this variant in a member of the core TRAPP subunit, TRAPPC4 that associates with vesicular trafficking and autophagy defects. This is the first report of a TRAPPC4 variant, and our findings add to the growing number of TRAPP-associated neurological disorders.

}, keywords = {Atrophy, Autophagy, Cerebellum, Cerebral Cortex, Child, Child, Preschool, Craniofacial Abnormalities, Deafness, Developmental Disabilities, Epilepsy, Female, Fibroblasts, Hearing Loss, Sensorineural, Humans, Infant, Infant, Newborn, Intellectual Disability, Male, Microcephaly, Microscopy, Fluorescence, Muscle Spasticity, Nerve Tissue Proteins, Neurodevelopmental Disorders, Pedigree, Quadriplegia, RNA Splice Sites, Syndrome, Vesicular Transport Proteins}, issn = {1460-2156}, doi = {10.1093/brain/awz374}, author = {Van Bergen, Nicole J and Guo, Yiran and Al-Deri, Noraldin and Lipatova, Zhanna and Stanga, Daniela and Zhao, Sarah and Murtazina, Rakhilya and Gyurkovska, Valeriya and Pehlivan, Davut and Mitani, Tadahiro and Gezdirici, Alper and Antony, Jayne and Collins, Felicity and Willis, Mary J H and Coban Akdemir, Zeynep H and Liu, Pengfei and Punetha, Jaya and Hunter, Jill V and Jhangiani, Shalini N and Fatih, Jawid M and Rosenfeld, Jill A and Posey, Jennifer E and Gibbs, Richard A and Karaca, Ender and Massey, Sean and Ranasinghe, Thisara G and Sleiman, Patrick and Troedson, Chris and Lupski, James R and Sacher, Michael and Segev, Nava and Hakonarson, Hakon and Christodoulou, John} } @article {337, title = {Loss of Nardilysin, a Mitochondrial Co-chaperone for α-Ketoglutarate Dehydrogenase, Promotes mTORC1 Activation and Neurodegeneration.}, journal = {Neuron}, volume = {93}, year = {2017}, month = {2017 Jan 04}, pages = {115-131}, abstract = {

We previously identified mutations in Nardilysin (dNrd1) in a forward genetic screen designed to isolate genes whose loss causes neurodegeneration in Drosophila photoreceptor neurons. Here~we show that NRD1 is localized to mitochondria, where it recruits mitochondrial chaperones and assists in the folding of α-ketoglutarate dehydrogenase (OGDH), a rate-limiting enzyme in~the Krebs cycle. Loss of Nrd1 or Ogdh leads to an increase in α-ketoglutarate, a substrate for OGDH,~which in turn leads to mTORC1 activation and a subsequent reduction in autophagy. Inhibition of mTOR activity by rapamycin or partially restoring autophagy delays neurodegeneration in dNrd1 mutant flies. In summary, this study reveals a novel role for NRD1 as a mitochondrial co-chaperone for OGDH and provides a mechanistic link between mitochondrial metabolic dysfunction, mTORC1 signaling, and impaired autophagy in neurodegeneration.

}, keywords = {Animals, Autophagy, Drosophila, Drosophila melanogaster, Drosophila Proteins, Ketoglutarate Dehydrogenase Complex, Ketoglutaric Acids, Lysine, Mechanistic Target of Rapamycin Complex 1, Metalloendopeptidases, Mitochondria, Molecular Chaperones, Multiprotein Complexes, Neurodegenerative Diseases, TOR Serine-Threonine Kinases}, issn = {1097-4199}, doi = {10.1016/j.neuron.2016.11.038}, author = {Yoon, Wan Hee and Sandoval, Hector and Nagarkar-Jaiswal, Sonal and Jaiswal, Manish and Yamamoto, Shinya and Haelterman, Nele A and Putluri, Nagireddy and Putluri, Vasanta and Sreekumar, Arun and Tos, Tulay and Aksoy, Ayse and Donti, Taraka and Graham, Brett H and Ohno, Mikiko and Nishi, Eiichiro and Hunter, Jill and Muzny, Donna M and Carmichael, Jason and Shen, Joseph and Arboleda, Valerie A and Nelson, Stanley F and Wangler, Michael F and Karaca, Ender and Lupski, James R and Bellen, Hugo J} } @article {179, title = {Biallelic mutations in SNX14 cause a syndromic form of cerebellar atrophy and lysosome-autophagosome dysfunction.}, journal = {Nat Genet}, volume = {47}, year = {2015}, month = {2015 May}, pages = {528-34}, abstract = {

Pediatric-onset ataxias often present clinically as developmental delay and intellectual disability, with prominent cerebellar atrophy as a key neuroradiographic finding. Here we describe a new clinically distinguishable recessive syndrome in 12 families with cerebellar atrophy together with ataxia, coarsened facial features and intellectual disability, due to truncating mutations in the sorting nexin gene SNX14, encoding a ubiquitously expressed modular PX domain-containing sorting factor. We found SNX14 localized to lysosomes and associated with phosphatidylinositol (3,5)-bisphosphate, a key component of late endosomes/lysosomes. Patient-derived cells showed engorged lysosomes and a slower autophagosome clearance rate upon autophagy induction by starvation. Zebrafish morphants for snx14 showed dramatic loss of cerebellar parenchyma, accumulation of autophagosomes and activation of apoptosis. Our results characterize a unique ataxia syndrome due to biallelic SNX14 mutations leading to lysosome-autophagosome dysfunction.

}, keywords = {Animals, Atrophy, Autophagy, Cerebellar Diseases, Cerebellum, Child, Preschool, Female, Gene Frequency, Humans, Infant, Lod Score, Lysosomal Storage Diseases, Lysosomes, Male, Mutation, Phagosomes, Sorting Nexins, Spinocerebellar Ataxias, Syndrome, Zebrafish}, issn = {1546-1718}, doi = {10.1038/ng.3256}, author = {Akizu, Naiara and Cantagrel, Vincent and Zaki, Maha S and Al-Gazali, Lihadh and Wang, Xin and Rosti, Rasim Ozgur and Dikoglu, Esra and Gelot, Antoinette Bernabe and Rosti, Basak and Vaux, Keith K and Scott, Eric M and Silhavy, Jennifer L and Schroth, Jana and Copeland, Brett and Schaffer, Ashleigh E and Gordts, Philip L S M and Esko, Jeffrey D and Buschman, Matthew D and Field, Seth J and Napolitano, Gennaro and Abdel-Salam, Ghada M and Ozgul, R Koksal and Sag{\i}roglu, Mahmut Samil and Azam, Matloob and Ismail, Samira and Aglan, Mona and Selim, Laila and Mahmoud, Iman G and Abdel-Hadi, Sawsan and Badawy, Amera El and Sadek, Abdelrahim A and Mojahedi, Faezeh and Kayserili, H{\"u}lya and Masri, Amira and Bastaki, Laila and Temtamy, Samia and M{\"u}ller, Ulrich and Desguerre, Isabelle and Casanova, Jean-Laurent and Dursun, Ali and G{\"u}nel, Murat and Gabriel, Stacey B and de Lonlay, Pascale and Gleeson, Joseph G} }