Autism spectrum disorder (ASD) represents a group of neurodevelopmental phenotypes with a strong genetic component. Excess of likely gene-disruptive (LGD) mutations of GIGYF1 was implicated in ASD. Here, we reported that GIGYF1 was the second most mutated gene among known ASD high-confidence risk genes. We investigated the inheritance of 46 GIGYF1 LGD variants, including the highly recurrent mutation, c.333del:p.L111Rfs*234. Inherited GIGYF1 heterozygous LGD variants were 1.8 times more common than de novo mutations. Unlike most high-confidence genes, ASD individuals with GIGYF1 LGD variants were less likely to have cognitive impairments. Using a Gigyf1 conditional knockout mouse model, we showed that haploinsufficiency in the developing brain led to social impairments without significant cognitive impairments. In contrast, homozygous mice showed more severe social disability as well as cognitive impairments. Gigyf1 deficiency in mice led to a reduction of upper layer cortical neurons accompanied by decreased proliferation and increased differentiation of neural progenitor cells. We showed that GIGYF1 regulated the recycling of IGF-1R to cell surface. Knockout of GIGYF1 led to a decreased level of IGF-1R on the cell surface disrupting the IGF-1R/ERK signaling pathway. In summary, our findings showed that GIGYF1 was a regulator of IGF-1R recycling. Haploinsufficiency of GIGYF1 was associated with autistic behaviors likely through interference with IGR-1R/ERK signaling pathway.
Guodong Chen, Bin Yu, Senwei Tan, Jieqiong Tan, Xiangbin Jia, Qiumeng Zhang, Xiaolei Zhang, Qian Jiang, Yue Hua, Yaoling Han, Shengjie Luo, Kendra Hoekzema, Raphael A. Bernier, Rachel K. Earl, Evangeline C. Kurtz-Nelson, Michaela J. Idleburg, Suneeta Madan Khetarpal, Rebecca Clark, Jessica Sebastian, Alberto Fernandez-Jaen, Sara Alvarez, Staci D. King, Luiza L.P. Ramos, Mara Lucia S.F. Santos, Donna M. Martin, Dan Brooks, Joseph D. Symonds, Ioana Cutcutache, Qian Pan, Zhengmao Hu, Ling Yuan, Evan E. Eichler, Kun Xia, Hui Guo
Mitochondrial stress triggers a response in the cell’s mitochondria and nucleus, but how these stress responses are coordinated in vivo is poorly understood. Here, we characterize a family with myopathy caused by a dominant p.G58R mutation in the mitochondrial protein CHCHD10. To understand the disease etiology, we developed a knock-in mouse model and found that mutant CHCHD10 aggregates in affected tissues, applying a toxic protein stress to the inner mitochondrial membrane. Unexpectedly, survival of CHCHD10 knock-in mice depended on a protective stress response mediated by OMA1. The OMA1 stress response acted both locally within mitochondria, causing mitochondrial fragmentation, and signaled outside the mitochondria, activating the integrated stress response through cleavage of DELE1. We additionally identified an isoform switch in the terminal complex of the electron transport chain as a component of this response. Our results demonstrate that OMA1 is critical for neonatal survival conditionally in the setting of inner mitochondrial membrane stress, coordinating local and global stress responses to reshape the mitochondrial network and proteome.
Mario K. Shammas, Xiaoping Huang, Beverly P. Wu, Evelyn Fessler, Insung Song, Nicholas P. Randolph, Yan Li, Christopher K.E. Bleck, Danielle A. Springer, Carl Fratter, Ines A. Barbosa, Andrew F. Powers, Pedro M. Quirós, Carlos Lopez-Otin, Lucas T. Jae, Joanna Poulton, Derek P. Narendra
Mitochondrial DNA (mtDNA) depletion/deletions syndromes (MDDS) encompass a clinically and etiologically heterogenous group of mitochondrial disorders due to impaired mtDNA maintenance. Among the most frequent causes of MDDS are defects in nucleoside/nucleotide metabolism, which is critical for synthesis and homeostasis of the deoxynucleoside triphosphate (dNTP) substrates of mtDNA replication. A central enzyme for generating dNTPs is ribonucleotide reductase, a critical mediator of de novo nucleotide synthesis composed of catalytic RRM1 subunits in complex with RRM2 or p53R2. Here, we report five probands from four families who presented with ptosis and ophthalmoplegia, plus other manifestations and multiple mtDNA deletions in muscle. We identified three RRM1 loss-of-function variants, including a dominant catalytic site variant (NP_001024.1: p.N427K) and two homozygous recessive variants at p.R381, which has evolutionarily conserved interactions with the specificity site. Atomistic molecular dynamics simulations indicate mechanisms by which RRM1 variants affect protein structure. Cultured primary skin fibroblasts of probands manifested mtDNA depletion under cycling conditions, indicating impaired de novo nucleotide synthesis. Fibroblasts also exhibited aberrant nucleoside diphosphate and dNTP pools and mtDNA ribonucleotide incorporation. Our data reveal primary RRM1 deficiency and, by extension, impaired de novo nucleotide synthesis are causes of MDDS.
Jonathan Shintaku, Wolfgang M. Pernice, Wafaa Eyaid, Jeevan B. GC, Zuben P. Brown, Marti Juanola-Falgarona, Javier Torres-Torronteras, Ewen W. Sommerville, Debby M.E.I. Hellebrekers, Emma L. Blakely, Alan Donaldson, Ingrid M.B.H. van de Laar, Cheng-Shiun Leu, Ramon Marti, Joachim Frank, Kurenai Tanji, David A. Koolen, Richard J. Rodenburg, Patrick F. Chinnery, H.J.M. Smeets, Gráinne S. Gorman, Penelope E. Bonnen, Robert W. Taylor, Michio Hirano
Many neurodegenerative disorders are caused by abnormal accumulation of misfolded proteins. In spinocerebellar ataxia type 1 (SCA1), accumulation of polyglutamine-expanded (polyQ-expanded) ataxin-1 (ATXN1) causes neuronal toxicity. Lowering total ATXN1, especially the polyQ-expanded form, alleviates disease phenotypes in mice, but the molecular mechanism by which the mutant ATXN1 is specifically modulated is not understood. Here, we identified 22 mutant ATXN1 regulators by performing a cross-species screen of 7787 and 2144 genes in human cells and Drosophila eyes, respectively. Among them, transglutaminase 5 (TG5) preferentially regulated mutant ATXN1 over the WT protein. TG enzymes catalyzed cross-linking of ATXN1 in a polyQ-length–dependent manner, thereby preferentially modulating mutant ATXN1 stability and oligomerization. Perturbing Tg in Drosophila SCA1 models modulated mutant ATXN1 toxicity. Moreover, TG5 was enriched in the nuclei of SCA1-affected neurons and colocalized with nuclear ATXN1 inclusions in brain tissue from patients with SCA1. Our work provides a molecular insight into SCA1 pathogenesis and an opportunity for allele-specific targeting for neurodegenerative disorders.
Won-Seok Lee, Ismael Al-Ramahi, Hyun-Hwan Jeong, Youjin Jang, Tao Lin, Carolyn J. Adamski, Laura A. Lavery, Smruti Rath, Ronald Richman, Vitaliy V. Bondar, Elizabeth Alcala, Jean-Pierre Revelli, Harry T. Orr, Zhandong Liu, Juan Botas, Huda Y. Zoghbi
BACKGROUND. Tuberous Sclerosis Complex (TSC) is a neurogenetic syndrome due to loss-of-function mutations in TSC2 or TSC1, characterized by tumors at multiple body sites, including facial angiofibroma (FAF). Here, an ultrasensitive assessment of the extent and range of UV-induced mutations in TSC facial skin was performed. METHODS. A Multiplex High-sensitivity PCR Assay (MHPA) was developed, enabling mutation detection at extremely low (<0.1%) variant allele frequencies (VAF). RESULTS. MHPA assays were developed for both TSC2 and TP53, and applied to 81 samples, including 66 skin biopsies. UV-induced second hit mutation causing inactivation of TSC2 was pervasive in TSC facial skin with an average of 4.8 mutations per 2 mm biopsy at median VAF 0.08%, generating >150,000 incipient facial tumors (subclinical ‘micro-FAFs’) in the average TSC subject. The MHPA analysis also led to the identification of a refined UV-related indel signature and a recurrent complex mutation pattern, consisting of both a single or dinucleotide variant, and a 1-9 nt deletion, in cis. CONCLUSION. TSC facial skin can be viewed as harboring a patchwork of clonal fibroblast proliferations (micro-FAF) with indolent growth, a small proportion of which develop into clinically observable FAF. Our observations also expand the spectrum of UV-related mutation signatures. FUNDING. This work was supported by the TSC Alliance, Engles Family Fund for Research in TSC and LAM, and National Institutes of Health, National Heart, Lung, and Blood Institute [U01HL131022-04; Intramural Research Program].
Katarzyna Klonowska, Joannes M. Grevelink, Krinio Giannikou, Barbara A. Ogorek, Zachary T. Herbert, Aaron R. Thorner, Thomas N. Darling, Joel Moss, David J. Kwiatkowski
Host defense and inflammation are regulated by the NF-κB essential modulator (NEMO), a scaffolding protein with a broad immune cell and tissue expression profile. Hypomorphic mutations in inhibitor of NF-κB kinase regulatory subunit gamma (IKBKG) encoding NEMO typically present with immunodeficiency. Here, we characterized a pediatric autoinflammatory syndrome in 3 unrelated male patients with distinct X-linked IKBKG germline mutations that led to overexpression of a NEMO protein isoform lacking the domain encoded by exon 5 (NEMO-Δex5). This isoform failed to associate with TANK binding kinase 1 (TBK1), and dermal fibroblasts from affected patients activated NF-κB in response to TNF but not TLR3 or RIG-I–like receptor (RLR) stimulation when isoform levels were high. By contrast, T cells, monocytes, and macrophages that expressed NEMO-Δex5 exhibited increased NF-κB activation and IFN production, and blood cells from these patients expressed a strong IFN and NF-κB transcriptional signature. Immune cells and TNF-stimulated dermal fibroblasts upregulated the inducible IKK protein (IKKi) that was stabilized by NEMO-Δex5, promoting type I IFN induction and antiviral responses. These data revealed how IKBKG mutations that lead to alternative splicing of skipping exon 5 cause a clinical phenotype we have named NEMO deleted exon 5 autoinflammatory syndrome (NDAS), distinct from the immune deficiency syndrome resulting from loss-of-function IKBKG mutations.
Younglang Lee, Alex W. Wessel, Jiazhi Xu, Julia G. Reinke, Eries Lee, Somin M. Kim, Amy P. Hsu, Jevgenia Zilberman-Rudenko, Sha Cao, Clinton Enos, Stephen R. Brooks, Zuoming Deng, Bin Lin, Adriana A. de Jesus, Daniel N. Hupalo, Daniela G.P. Piotto, Maria T. Terreri, Victoria R. Dimitriades, Clifton L. Dalgard, Steven M. Holland, Raphaela Goldbach-Mansky, Richard M. Siegel, Eric P. Hanson
Genetic variants at the SORT1 locus in humans causing increased SORT1 expression in liver are significantly associated with reduced plasma levels of LDL cholesterol and apolipoprotein B (apoB). However, the role of hepatic sortilin remains controversial, as genetic deletion of sortilin in mice has yielded variable and conflicting effects on apoB secretion. Sort1 knockout mice on a chow diet and several Sort1-deficient hepatocyte lines displayed no difference in apoB secretion. When these models were challenged with high fat or ER stress, the loss of Sort1 expression resulted in a significant increase in apoB-100 secretion. Sort1 overexpression studies yielded reciprocal results. Importantly, diabetic carriers of SORT1 variant have larger decreases in plasma apoB, TG, and VLDL and LDL particle number as compared to non-diabetics with the same variants. We conclude that under basal non-stressed conditions, loss of sortilin has little effect on hepatocyte apoB secretion, but that in the setting of lipid-loading or ER stress, sortilin deficiency leads to increased apoB secretion. These results are consistent with the directionality of effect in human genetics studies and suggest that under stress conditions, hepatic sortilin directs apoB toward lysosomal degradation rather than secretion, potentially serving as a quality control step in the apoB secretion pathway in hepatocytes.
Donna M. Conlon, Carolin V. Schneider, Yi-An Ko, Amrith Rodrigues, Kathy Guo, Nicholas J. Hand, Daniel J. Rader
Despite being the first homolog of the bacterial RecQ helicase to be identified in humans the function of RECQL1 remains poorly characterised. Furthermore, unlike other members of the human RECQ family of helicases, mutations in RECQL1 have not been associated with a genetic disease. Here we identify two families with a novel genome instability disorder, named RECON (RECql ONe) Syndrome caused by biallelic mutations in the RECQL gene. The affected individuals exhibit short stature, progeroid facial features, a hypoplastic nose, xeroderma and skin photosensitivity. Affected individuals were homozygous for the same missense mutation in RECQL1 (p.Ala459Ser) located within its zinc binding domain. Biochemical analysis of the mutant RECQL1 protein revealed that the p.A459S missense mutation compromised its ATPase, helicase and fork restoration activity, whilst its capacity to promote single-strand DNA annealing was largely unaffected. At the cellular level, this mutation in RECQL1 gave rise to a defect in the ability to repair DNA damage induced by exposure to topoisomerase poisons and a failure of DNA replication to progress efficiently in the presence of abortive topoisomerase lesions. Taken together, RECQL1 is the fourth member of the RecQ family of helicases to be associated with a human genome instability disorder.
Bassam Abu-Libdeh, Satpal S. Jhujh, Srijita Dhar, Joshua A. Sommers, Arindam Datta, Gabriel M.C. Longo, Laura J. Grange, John J. Reynolds, Sophie L. Cooke, Gavin S. McNee, Robert Hollingworth, Beth L. Woodward, Anil N. Ganesh, Stephen J. Smerdon, Claudia M. Nicolae, Karina Durlacher-Betzer, Vered Molho-Pessach, Abdulsalam Abu-Libdeh, Vardiella Meiner, George-Lucian Moldovan, Vassilis Roukos, Tamar Harel, Robert M. Brosh Jr., Grant S. Stewart
Inherited germline mutations in the BRCA1 (BReast CAncer gene 1) or BRCA2 (BReast CAncer gene 2) genes (herein BRCA1/2) greatly increase the risk of breast and ovarian cancer, presumably by elevating somatic mutational errors as a consequence of deficient DNA repair. However, this has never been directly demonstrated by a comprehensive analysis of the somatic mutational landscape of primary, non-cancer, mammary epithelial cells of women diagnosed with pathogenic BRCA1 or BRCA2 germline mutations. Here we used an accurate, single-cell whole genome sequencing approach to first show that telomerized primary mammary epithelial cells heterozygous for a highly penetrant BRCA1 variant displayed a robustly elevated mutation frequency as compared to their isogenic control cells. We then demonstrated a small but statistically significant increase in mutation frequency in mammary epithelial cells isolated from the breast of BRCA1/2 mutation carriers as compared to those obtained from age-matched controls with no genetically increased risk for breast cancer.
Shixiang Sun, Kristina Brazhnik, Moonsook Lee, Alexander Y. Maslov, Yi Zhang, Zhenqiu Huang, Susan Klugman, Ben H. Park, Jan Vijg, Cristina Montagna
The KRAS proto-oncogene is among the most frequently mutated genes in cancer, yet for 40 years it remained an elusive therapeutic target. Recently, allosteric inhibitors that covalently bind to KRAS G12C mutations have been approved for use in lung adenocarcinomas. Although responses are observed they are often short-lived, thus making in-depth characterization of the mechanisms of resistance of paramount importance. Here, we present a rapid-autopsy case of a patient who had a KRASG12C-mutant lung adenocarcinoma who initially responded to a KRAS G12C inhibitor but then rapidly developed resistance. Using deep RNA and whole exome sequencing comparing pre-treatment, post-treatment and matched normal tissues, we uncover numerous mechanisms of resistance to direct KRAS inhibition. In addition to decreased KRAS G12C mutant allele frequency in refractory tumors, we also found reactivation of the MAPK pathway despite no new mutations in KRAS or its downstream mediators. Tumor cell intrinsic and non-cell autonomous mechanisms included increased complement activation, coagulation and tumor angiogenesis, and several lines of evidence of immunologic evasion. Together, our findings reveal numerous mechanisms of resistance to current KRAS G12C inhibitors through enrichment of clonal populations, KRAS-independent downstream signaling and diverse remodeling of the tumor microenvironment.
Yihsuan S. Tsai, Mark G. Woodcock, Salma H. Azam, Leigh B. Thorne, Krishna L. Kanchi, Joel S. Parker, Benjamin G Vincent, Chad V. Pecot