@article {769, title = {Delineation of a Human Mendelian Disorder of the DNA Demethylation Machinery: TET3 Deficiency.}, journal = {Am J Hum Genet}, volume = {106}, year = {2020}, month = {2020 02 06}, pages = {234-245}, abstract = {

Germline pathogenic variants in chromatin-modifying enzymes are a common cause of pediatric developmental disorders. These enzymes catalyze reactions that regulate epigenetic inheritance via histone post-translational modifications and DNA methylation. Cytosine methylation (5-methylcytosine [5mC]) of DNA is the quintessential epigenetic mark, yet no human Mendelian disorder of DNA demethylation has yet been delineated. Here, we describe in detail a Mendelian disorder caused by the disruption of DNA demethylation. TET3 is a methylcytosine dioxygenase that initiates DNA demethylation during early zygote formation, embryogenesis, and neuronal differentiation and is intolerant to haploinsufficiency in mice and humans. We identify and characterize 11 cases of human TET3 deficiency in eight families with the common phenotypic features of intellectual disability and/or global developmental delay; hypotonia; autistic traits; movement disorders; growth abnormalities; and facial dysmorphism. Mono-allelic frameshift and nonsense variants in TET3 occur throughout the coding region. Mono-allelic and bi-allelic missense variants localize to conserved residues; all but one such variant occur within the catalytic domain, and most display hypomorphic function in an assay of catalytic activity. TET3 deficiency and other Mendelian disorders of the epigenetic machinery show substantial phenotypic overlap, including features of intellectual disability and abnormal growth, underscoring shared disease mechanisms.

}, keywords = {Adult, Amino Acid Sequence, Autistic Disorder, Child, Child, Preschool, Developmental Disabilities, Dioxygenases, DNA Demethylation, Embryonic Development, Female, Gene Expression Regulation, Developmental, Growth Disorders, Humans, Infant, Male, Middle Aged, Movement Disorders, Pedigree, Protein Conformation, Sequence Homology, Young Adult}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2019.12.007}, author = {Beck, David B and Petracovici, Ana and He, Chongsheng and Moore, Hannah W and Louie, Raymond J and Ansar, Muhammad and Douzgou, Sofia and Sithambaram, Sivagamy and Cottrell, Trudie and Santos-Cortez, Regie Lyn P and Prijoles, Eloise J and Bend, Renee and Keren, Boris and Mignot, Cyril and Nougues, Marie-Christine and {\~O}unap, Katrin and Reimand, Tiia and Pajusalu, Sander and Zahid, Muhammad and Saqib, Muhammad Arif Nadeem and Buratti, Julien and Seaby, Eleanor G and McWalter, Kirsty and Telegrafi, Aida and Baldridge, Dustin and Shinawi, Marwan and Leal, Suzanne M and Schaefer, G Bradley and Stevenson, Roger E and Banka, Siddharth and Bonasio, Roberto and Fahrner, Jill A} } @article {498, title = {Novel candidate genes and variants underlying autosomal recessive neurodevelopmental disorders with intellectual disability.}, journal = {Hum Genet}, volume = {137}, year = {2018}, month = {2018 Sep}, pages = {735-752}, abstract = {

Identification of Mendelian genes for neurodevelopmental disorders using exome sequencing to study autosomal recessive (AR) consanguineous pedigrees has been highly successful. To identify causal variants for syndromic and non-syndromic intellectual disability (ID), exome sequencing was performed using DNA samples from 22 consanguineous Pakistani families with ARID, of which 21 have additional phenotypes including microcephaly. To aid in variant identification, homozygosity mapping and linkage analysis were performed. DNA samples from affected family member(s) from every pedigree underwent exome sequencing. Identified rare damaging exome variants were tested for co-segregation with ID using Sanger sequencing. For seven ARID families, variants were identified in genes not previously associated with ID, including: EI24, FXR1 and TET3 for which knockout mouse models have brain defects; and CACNG7 and TRAPPC10 where cell studies suggest roles in important neural pathways. For two families, the novel ARID genes CARNMT1 and GARNL3 lie within previously reported ID microdeletion regions. We also observed homozygous variants in two ID candidate genes, GRAMD1B and TBRG1, for which each has been previously reported in a single family. An additional 14 families have homozygous variants in established ID genes, of which 11 variants are novel. All ARID genes have increased expression in specific structures of the developing and adult human brain and 91\% of the genes are differentially expressed in utero or during early childhood. The identification of novel ARID candidate genes and variants adds to the knowledge base that is required to further understand human brain function and development.

}, keywords = {Adult, Consanguinity, Family, Female, Genes, Recessive, Genetic Markers, Humans, Intellectual Disability, Male, Middle Aged, Mutation, Neurodevelopmental Disorders, Pedigree}, issn = {1432-1203}, doi = {10.1007/s00439-018-1928-6}, author = {Santos-Cortez, Regie Lyn P and Khan, Valeed and Khan, Falak Sher and Mughal, Zaib-Un-Nisa and Chakchouk, Imen and Lee, Kwanghyuk and Rasheed, Memoona and Hamza, Rifat and Acharya, Anushree and Ullah, Ehsan and Saqib, Muhammad Arif Nadeem and Abbe, Izoduwa and Ali, Ghazanfar and Hassan, Muhammad Jawad and Khan, Saadullah and Azeem, Zahid and Ullah, Irfan and Bamshad, Michael J and Nickerson, Deborah A and Schrauwen, Isabelle and Ahmad, Wasim and Ansar, Muhammad and Leal, Suzanne M} } @article {157, title = {Mutation of ATF6 causes autosomal recessive achromatopsia.}, journal = {Hum Genet}, volume = {134}, year = {2015}, month = {2015 Sep}, pages = {941-50}, abstract = {

Achromatopsia (ACHM) is an early-onset retinal dystrophy characterized by photophobia, nystagmus, color blindness and severely reduced visual acuity. Currently mutations in five genes CNGA3, CNGB3, GNAT2, PDE6C and PDE6H have been implicated in ACHM. We performed homozygosity mapping and linkage analysis in a consanguineous Pakistani ACHM family and mapped the locus to a 15.12-Mb region on chromosome 1q23.1-q24.3 with a maximum LOD score of 3.6. A DNA sample from an affected family member underwent exome sequencing. Within the ATF6 gene, a single-base insertion variant c.355_356dupG (p.Glu119Glyfs*8) was identified, which completely segregates with the ACHM phenotype within the family. The frameshift variant was absent in public variant databases, in 130 exomes from unrelated Pakistani individuals, and in 235 ethnically matched controls. The variant is predicted to result in a truncated protein that lacks the DNA binding and transmembrane domains and therefore affects the function of ATF6 as a transcription factor that initiates the unfolded protein response during endoplasmic reticulum (ER) stress. Immunolabeling with anti-ATF6 antibodies showed localization throughout the mouse neuronal retina, including retinal pigment epithelium, photoreceptor cells, inner nuclear layer, inner and outer plexiform layers, with a more prominent signal in retinal ganglion cells. In contrast to cytoplasmic expression of wild-type protein, in heterologous cells ATF6 protein with the p.Glu119Glyfs*8 variant is mainly confined to the nucleus. Our results imply that response to ER stress as mediated by the ATF6 pathway is essential for color vision in humans.

}, keywords = {Activating Transcription Factor 6, Adolescent, Animals, Asian Continental Ancestry Group, Color Vision Defects, Consanguinity, DNA Mutational Analysis, Exome, Female, Frameshift Mutation, Genotyping Techniques, Homozygote, Humans, Limit of Detection, Male, Mice, Mice, Inbred C57BL, Pakistan, Pedigree, Phenotype, Retina, Signal Transduction}, issn = {1432-1203}, doi = {10.1007/s00439-015-1571-4}, author = {Ansar, Muhammad and Santos-Cortez, Regie Lyn P and Saqib, Muhammad Arif Nadeem and Zulfiqar, Fareeha and Lee, Kwanghyuk and Ashraf, Naeem Mahmood and Ullah, Ehsan and Wang, Xin and Sajid, Sundus and Khan, Falak Sher and Amin-ud-Din, Muhammad and Smith, Joshua D and Shendure, Jay and Bamshad, Michael J and Nickerson, Deborah A and Hameed, Abdul and Riazuddin, Saima and Ahmed, Zubair M and Ahmad, Wasim and Leal, Suzanne M} }