@article {941, title = {MED27 Variants Cause Developmental Delay, Dystonia, and Cerebellar Hypoplasia.}, journal = {Ann Neurol}, volume = {89}, year = {2021}, month = {2021 04}, pages = {828-833}, abstract = {

The Mediator multiprotein complex functions as a regulator of RNA polymerase II-catalyzed gene transcription. In this study, exome sequencing detected biallelic putative disease-causing variants in MED27, encoding Mediator complex subunit 27, in 16 patients from 11 families with a novel neurodevelopmental syndrome. Patient phenotypes are highly homogeneous, including global developmental delay, intellectual disability, axial hypotonia with distal spasticity, dystonic movements, and cerebellar hypoplasia. Seizures and cataracts were noted in severely affected individuals. Identification of multiple patients with biallelic MED27 variants supports the critical role of MED27 in normal human neural development, particularly for the cerebellum. ANN NEUROL 2021;89:828-833.

}, keywords = {Adolescent, Adult, Amino Acid Sequence, Cataract, Cerebellum, Child, Child, Preschool, Developmental Disabilities, Dystonia, Epilepsy, Genetic Variation, Humans, Infant, Mediator Complex, Nervous System Malformations, Phenotype, Whole Exome Sequencing}, issn = {1531-8249}, doi = {10.1002/ana.26019}, author = {Meng, Linyan and Isohanni, Pirjo and Shao, Yunru and GrAHm, Brett H and Hickey, Scott E and Brooks, Stephanie and Suomalainen, Anu and Joset, Pascal and Steindl, Katharina and Rauch, Anita and Hackenberg, Annette and High, Frances A and Armstrong-Javors, Amy and Mencacci, Niccol{\`o} E and Gonz{\`a}lez-Latapi, Paulina and Kamel, Walaa A and Al-Hashel, Jasem Y and Bustos, Bernab{\'e} I and Hernandez, Alejandro V and Krainc, Dimitri and Lubbe, Steven J and Van Esch, Hilde and De Luca, Chiara and Ballon, Katleen and Ravelli, Claudia and Burglen, Lydie and Qebibo, Leila and Calame, Daniel G and Mitani, Tadahiro and Marafi, Dana and Pehlivan, Davut and Saadi, Nebal W and Sahin, Yavuz and Maroofian, Reza and Efthymiou, Stephanie and Houlden, Henry and Maqbool, Shazia and Rahman, Fatima and Gu, Shen and Posey, Jennifer E and Lupski, James R and Hunter, Jill V and Wangler, Michael F and Carroll, Christopher J and Yang, Yaping} } @article {1014, title = {Neurodevelopmental disorder in an Egyptian family with a biallelic ALKBH8 variant.}, journal = {Am J Med Genet A}, volume = {185}, year = {2021}, month = {2021 04}, pages = {1288-1293}, abstract = {

Alkylated DNA repair protein AlkB homolog 8 (ALKBH8) is a member of the AlkB family of dioxygenases. ALKBH8 is a methyltransferase of the highly variable wobble nucleoside position in the anticodon loop of tRNA and thus plays a critical role in tRNA modification by preserving codon recognition and preventing errors in amino acid incorporation during translation. Moreover, its activity catalyzes uridine modifications that are proposed to be critical for accurate protein translation. Previously, two distinct homozygous truncating variants in the final exon of ALKBH8 were described in two unrelated large Saudi Arabian kindreds with intellectual developmental disorder and autosomal recessive 71 (MRT71) syndrome (MIM$\#$ 618504). Here, we report a third family-of Egyptian descent-harboring a novel homozygous frame-shift variant in the last exon of ALKBH8. Two affected siblings in this family exhibit global developmental delay and intellectual disability as shared characteristic features of MRT71 syndrome, and we further characterize their observed dysmorphic features and brain MRI findings. This description of a third family with a truncating ALKBH8 variant from a distinct population broadens the phenotypic and genotypic spectrum of MRT71 syndrome, affirms that perturbations in tRNA biogenesis can contribute to neurogenetic disease traits, and firmly establishes ALKBH8 as a novel neurodevelopmental disease gene.

}, issn = {1552-4833}, doi = {10.1002/ajmg.a.62100}, author = {Saad, Ahmed K and Marafi, Dana and Mitani, Tadahiro and Du, Haowei and Rafat, Karima and Fatih, Jawid M and Jhangiani, Shalini N and Coban-Akdemir, Zeynep and Gibbs, Richard A and Pehlivan, Davut and Hunter, Jill V and Posey, Jennifer E and Zaki, MAH S and Lupski, James R} } @article {1015, title = {A novel homozygous SLC13A5 whole-gene deletion generated by Alu/Alu-mediated rearrangement in an Iraqi family with epileptic encephalopathy.}, journal = {Am J Med Genet A}, year = {2021}, month = {2021 Apr 02}, abstract = {

Biallelic loss-of-function (LoF) of SLC13A5 (solute carrier family 13, member 5) induced deficiency in sodium/citrate transporter (NaCT) causes autosomal recessive developmental epileptic encephalopathy 25 with hypoplastic amelogenesis imperfecta (DEE25; MIM $\#$615905). Many pathogenic SLC13A5 single nucleotide variants (SNVs) and small indels have been described; however, no cases with copy number variants (CNVs) have been sufficiently investigated. We describe a consanguineous Iraqi family harboring an 88.5 kb homozygous deletion including SLC13A5 in Chr17p13.1. The three affected male siblings exhibit neonatal-onset epilepsy with fever-sensitivity, recurrent status epilepticus, global developmental delay/intellectual disability (GDD/ID), and other variable neurological findings as shared phenotypical features of DEE25. Two of the three affected subjects exhibit hypoplastic amelogenesis imperfecta (AI), while the proband shows no evidence of dental abnormalities or AI at 2 years of age with apparently unaffected primary dentition. Characterization of the genomic architecture at this locus revealed evidence for genomic instability generated by an Alu/Alu-mediated rearrangement; confirmed by break-point junction Sanger sequencing. This multiplex family from a distinct population elucidates the phenotypic consequence of complete LoF of SLC13A5 and illustrates the importance of read-depth-based CNV detection in comprehensive exome sequencing analysis to solve cases that otherwise remain molecularly unsolved.

}, issn = {1552-4833}, doi = {10.1002/ajmg.a.62192}, author = {Duan, Ruizhi and Saadi, Nebal Waill and Grochowski, Christopher M and Bhadila, Ghalia and Faridoun, Afnan and Mitani, Tadahiro and Du, Haowei and Fatih, Jawid M and Jhangiani, Shalini N and Akdemir, Zeynep C and Gibbs, Richard A and Pehlivan, Davut and Posey, Jennifer E and Marafi, Dana and Lupski, James R} } @article {1026, title = {Two novel bi-allelic KDELR2 missense variants cause osteogenesis imperfecta with neurodevelopmental features.}, journal = {Am J Med Genet A}, year = {2021}, month = {2021 May 08}, issn = {1552-4833}, doi = {10.1002/ajmg.a.62221}, author = {Efthymiou, Stephanie and Herman, Isabella and Rahman, Fatima and Anwar, Najwa and Maroofian, Reza and Yip, Janice and Mitani, Tadahiro and Calame, Daniel G and Hunter, Jill V and Sutton, V Reid and Yilmaz Gulec, Elif and Duan, Ruizhi and Fatih, Jawid M and Marafi, Dana and Pehlivan, Davut and Jhangiani, Shalini N and Gibbs, Richard A and Posey, Jennifer E and Maqbool, Shazia and Lupski, James R and Houlden, Henry} } @article {758, title = {Biallelic GRM7 variants cause epilepsy, microcephaly, and cerebral atrophy.}, journal = {Ann Clin Transl Neurol}, volume = {7}, year = {2020}, month = {2020 05}, pages = {610-627}, abstract = {

OBJECTIVE: Defects in ion channels and neurotransmitter receptors are implicated in developmental and epileptic encephalopathy (DEE). Metabotropic glutamate receptor 7 (mGluR7), encoded by GRM7, is a presynaptic G-protein-coupled glutamate receptor critical for synaptic transmission. We previously proposed GRM7 as a candidate disease gene in two families with neurodevelopmental disorders (NDDs). One additional family has been published since. Here, we describe three additional families with GRM7 biallelic variants and deeply characterize the associated clinical neurological and electrophysiological phenotype and molecular data in 11 affected individuals from six unrelated families.

METHODS: Exome sequencing and family-based rare variant analyses on a cohort of 220 consanguineous families with NDDs revealed three families with GRM7 biallelic variants; three additional families were identified through literature search and collaboration with a clinical molecular laboratory.

RESULTS: We compared the observed clinical features and variants of 11 affected individuals from the six unrelated families. Identified novel deleterious variants included two homozygous missense variants (c.2671G>A:p.Glu891Lys and c.1973G>A:p.Arg685Gln) and one homozygous stop-gain variant (c.1975C>T:p.Arg659Ter). Developmental delay, neonatal- or infantile-onset epilepsy, and microcephaly were universal. Three individuals had hypothalamic-pituitary-axis dysfunction without pituitary structural abnormality. Neuroimaging showed cerebral atrophy and hypomyelination in a majority of cases. Two siblings demonstrated progressive loss of myelination by 2~years in both and an acquired microcephaly pattern in one. Five individuals died in early or late childhood.

CONCLUSION: Detailed clinical characterization of 11 individuals from six unrelated families demonstrates that rare biallelic GRM7 pathogenic variants can cause DEEs, microcephaly, hypomyelination, and cerebral atrophy.

}, keywords = {Adolescent, Alleles, Atrophy, Child, Child, Preschool, Cohort Studies, Consanguinity, Epilepsy, Female, Humans, Infant, Male, Microcephaly, Neurodevelopmental Disorders, Pedigree, Phenotype, Receptors, Metabotropic Glutamate, Whole Exome Sequencing}, issn = {2328-9503}, doi = {10.1002/acn3.51003}, author = {Marafi, Dana and Mitani, Tadahiro and Isikay, Sedat and Hertecant, Jozef and Almannai, Mohammed and Manickam, Kandamurugu and Abou Jamra, Rami and El-Hattab, Ayman W and Rajah, Jaishen and Fatih, Jawid M and Du, Haowei and Karaca, Ender and Bayram, Yavuz and Punetha, Jaya and Rosenfeld, Jill A and Jhangiani, Shalini N and Boerwinkle, Eric and Akdemir, Zeynep C and Erdin, Serkan and Hunter, Jill V and Gibbs, Richard A and Pehlivan, Davut and Posey, Jennifer E and Lupski, James R} } @article {945, title = {Biallelic in-frame deletion in TRAPPC4 in a family with developmental delay and cerebellar atrophy.}, journal = {Brain}, volume = {143}, year = {2020}, month = {2020 10 01}, pages = {e83}, keywords = {Atrophy, Cerebellar Diseases, Humans, Intellectual Disability, Sequence Deletion}, issn = {1460-2156}, doi = {10.1093/brain/awaa256}, author = {Saad, Ahmed K and Marafi, Dana and Mitani, Tadahiro and Jolly, Angad and Du, Haowei and Elbendary, Hasnaa M and Jhangiani, Shalini N and Akdemir, Zeynep C and Gibbs, Richard A and Hunter, Jill V and Carvalho, Claudia M B C and Pehlivan, Davut and Posey, Jennifer E and Zaki, MAH S and Lupski, James R} } @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 {854, title = {Phenotypic expansion in KIF1A-related dominant disorders: A description of novel variants and review of published cases.}, journal = {Hum Mutat}, volume = {41}, year = {2020}, month = {2020 12}, pages = {2094-2104}, abstract = {

KIF1A is a molecular motor for membrane-bound cargo important to the development and survival of sensory neurons. KIF1A dysfunction has been associated with several Mendelian disorders with a spectrum of overlapping phenotypes, ranging from spastic paraplegia to intellectual disability. We present a novel pathogenic in-frame deletion in the KIF1A molecular motor domain inherited by two affected siblings from an unaffected mother with apparent germline mosaicism. We identified eight additional cases with heterozygous, pathogenic KIF1A variants ascertained from a local data lake. Our data provide evidence for the expansion of KIF1A-associated phenotypes to include hip subluxation and dystonia~as well as phenotypes observed in only a single case: gelastic cataplexy, coxa valga, and double collecting system. We review the literature and suggest that KIF1A dysfunction is better understood as a single neuromuscular disorder with variable involvement of other organ systems than a set of discrete disorders converging at a single locus.

}, issn = {1098-1004}, doi = {10.1002/humu.24118}, author = {Montenegro-Garreaud, Ximena and Hansen, Adam W and Khayat, Michael M and Chander, Varuna and Grochowski, Christopher M and Jiang, Yunyun and Li, He and Mitani, Tadahiro and Kessler, Elena and Jayaseelan, Joy and Shen, Hua and Gezdirici, Alper and Pehlivan, Davut and Meng, Qingchang and Rosenfeld, Jill A and Jhangiani, Shalini N and Madan-Khetarpal, Suneeta and Scott, Daryl A and Abarca-Barriga, Hugo and Trubnykova, Milana and Gingras, Marie-Claude and Muzny, Donna M and Posey, Jennifer E and Liu, Pengfei and Lupski, James R and Gibbs, Richard A} } @article {716, title = {Homozygous Missense Variants in NTNG2, Encoding a Presynaptic Netrin-G2 Adhesion Protein, Lead to a Distinct Neurodevelopmental Disorder.}, journal = {Am J Hum Genet}, volume = {105}, year = {2019}, month = {2019 Nov 07}, pages = {1048-1056}, abstract = {

NTNG2 encodes netrin-G2, a membrane-anchored protein implicated in the molecular organization of neuronal circuitry and synaptic organization and diversification in vertebrates. In this study, through a combination of exome sequencing and autozygosity mapping, we have identified 16 individuals (from seven unrelated families) with ultra-rare homozygous missense variants in NTNG2; these individuals present with shared features of a neurodevelopmental disorder consisting of global developmental delay, severe to profound intellectual disability, muscle weakness and abnormal tone, autistic features, behavioral abnormalities, and variable dysmorphisms. The variants disrupt highly conserved residues across the protein. Functional experiments, including in silico analysis of the protein structure, in~vitro assessment of cell surface expression, and in~vitro knockdown, revealed potential mechanisms of pathogenicity of the variants, including loss of protein function and decreased neurite outgrowth. Our data indicate that appropriate expression of NTNG2 plays an important role in neurotypical development.

}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2019.09.025}, author = {Dias, Caroline M and Punetha, Jaya and Zheng, C{\'e}line and Mazaheri, Neda and Rad, Abolfazl and Efthymiou, Stephanie and Petersen, Andrea and Dehghani, Mohammadreza and Pehlivan, Davut and Partlow, Jennifer N and Posey, Jennifer E and Salpietro, Vincenzo and Gezdirici, Alper and Malamiri, Reza Azizi and Al Menabawy, Nihal M and Selim, Laila A and Vahidi Mehrjardi, Mohammad Yahya and Banu, Selina and Polla, Daniel L and Yang, Edward and Rezazadeh Varaghchi, Jamileh and Mitani, Tadahiro and van Beusekom, Ellen and Najafi, Maryam and Sedaghat, Alireza and Keller-Ramey, Jennifer and Durham, Leslie and Coban-Akdemir, Zeynep and Karaca, Ender and Orlova, Valeria and Schaeken, Lieke L M and Sherafat, Amir and Jhangiani, Shalini N and Stanley, Valentina and Shariati, Gholamreza and Galehdari, Hamid and Gleeson, Joseph G and Walsh, Christopher A and Lupski, James R and Seiradake, Elena and Houlden, Henry and van Bokhoven, Hans and Maroofian, Reza} }