Genetics
Abstract
Mutations of CNTNAP1 were associated with myelination disorders, suggesting the role of CNTNAP1 in myelination processes. Whether CNTNAP1 may have a role in early cortical neuronal development is largely unknown. In this study, we identified 4 compound heterozygous mutations of CNTNAP1 in 2 Chinese families. Using mouse models, we found that CNTNAP1 is highly expressed in neurons and is located predominantly in MAP2+ neurons during the early developmental stage. Importantly, Cntnap1 deficiency results in aberrant dendritic growth and spine development in vitro and in vivo, and it delayed migration of cortical neurons during early development. Finally, we found that the number of parvalbumin+ neurons in the cortex and hippocampus of Cntnap1–/– mice is strikingly increased by P15, suggesting that excitation/inhibition balance is impaired. Together, this evidence elucidates a critical function of CNTNAP1 in cortical development, providing insights underlying molecular and circuit mechanisms of CNTNAP1-related disease.
Authors
Wanxing Li, Lin Yang, Chuanqing Tang, Kaiyi Liu, Yulan Lu, Huijun Wang, Kai Yan, Zilong Qiu, Wenhao Zhou
Abstract
Complex I (also known as NADH-ubiquinone oxidoreductase) deficiency is the most frequent mitochondrial disorder present in childhood. NADH-ubiquinone oxidoreductase iron-sulfur protein 3 (NDUFS3) is a catalytic subunit of the mitochondrial complex I; NDUFS3 is conserved from bacteria and essential for complex I function. Mutations affecting complex I, including in the Ndufs3 gene, cause fatal neurodegenerative diseases, such as Leigh syndrome. No treatment is available for these conditions. We developed and performed a detailed molecular characterization of a neuron-specific Ndufs3 conditional KO mouse model. We showed that deletion of Ndufs3 in forebrain neurons reduced complex I activity, altered brain energy metabolism, and increased locomotor activity with impaired motor coordination, balance, and stereotyped behavior. Metabolomics analyses showed an increase of glycolysis intermediates, suggesting an adaptive response to the complex I defect. Administration of metformin to these mice delayed the onset of the neurological symptoms but not of neuronal loss. This improvement was likely related to enhancement of glucose uptake and utilization, which are known effects of metformin in the brain. Despite reports that metformin inhibits complex I activity, our findings did not show worsening a complex I defect nor increases in lactic acid, suggesting that metformin should be further evaluated for use in patients with mitochondrial encephalopathies.
Authors
Susana Peralta, Milena Pinto, Tania Arguello, Sofia Garcia, Francisca Diaz, Carlos T. Moraes
Abstract
Phenylalanine hydroxylase–deficient (PAH-deficient) phenylketonuria (PKU) results in systemic hyperphenylalaninemia, leading to neurotoxicity with severe developmental disabilities. Dietary phenylalanine (Phe) restriction prevents the most deleterious effects of hyperphenylalaninemia, but adherence to diet is poor in adult and adolescent patients, resulting in characteristic neurobehavioral phenotypes. Thus, an urgent need exists for new treatments. Additionally, rodent models of PKU do not adequately reflect neurocognitive phenotypes, and thus there is a need for improved animal models. To this end, we have developed PAH-null pigs. After selection of optimal CRISPR/Cas9 genome-editing reagents by using an in vitro cell model, zygote injection of 2 sgRNAs and Cas9 mRNA demonstrated deletions in preimplantation embryos, with embryo transfer to a surrogate leading to 2 founder animals. One pig was heterozygous for a PAH exon 6 deletion allele, while the other was compound heterozygous for deletions of exon 6 and of exons 6–7. The affected pig exhibited hyperphenylalaninemia (2000–5000 μM) that was treatable by dietary Phe restriction, consistent with classical PKU, along with juvenile growth retardation, hypopigmentation, ventriculomegaly, and decreased brain gray matter volume. In conclusion, we have established a large-animal preclinical model of PKU to investigate pathophysiology and to assess new therapeutic interventions.
Authors
Erik A. Koppes, Bethany K. Redel, Marie A. Johnson, Kristen J. Skvorak, Lina Ghaloul-Gonzalez, Megan E. Yates, Dale W. Lewis, Susanne M. Gollin, Yijen L. Wu, Shawn E. Christ, Martine Yerle, Angela Leshinski, Lee D. Spate, Joshua A. Benne, Stephanie L. Murphy, Melissa S. Samuel, Eric M. Walters, Sarah A. Hansen, Kevin D. Wells, Uta Lichter-Konecki, Robert A. Wagner, Joseph T. Newsome, Steven F. Dobrowolski, Jerry Vockley, Randall S. Prather, Robert D. Nicholls
Abstract
Somatic KRAS mutations are highly prevalent in many human cancers. In addition, a distinct spectrum of germline KRAS mutations cause developmental disorders called RASopathies. The mutant proteins encoded by these germline KRAS mutations are less biochemically and functionally activated than the mutant proteins found in cancer. We generated mice harboring conditional KrasLSL-P34R and KrasLSL-T58I “knock in” alleles and characterized the consequences of each mutation in vivo. Embryonic expression of KrasT58I resulted in craniofacial abnormalities reminiscent of RASopathy disorders, and these mice also exhibited hyperplastic growth of multiple organs, modest alterations in cardiac valvulogenesis, myocardial hypertrophy, and myeloproliferation. By contrast, embryonic KrasP34R expression resulted in early perinatal lethality from respiratory failure due to defective lung sacculation, which was associated with aberrant ERK activity in lung epithelial cells. Somatic Mx1-Cre-mediated activation in the hematopoietic compartment showed that KrasP34R and KrasT58I expression had distinct signaling effects despite causing a similar spectrum of hematologic diseases. These novel mouse strains are robust models for investigating the consequences of endogenous hyperactive K-Ras signaling in different developing and adult tissues, for comparing how oncogenic and germline K-Ras proteins perturb signaling networks and cell fate decisions, and for performing preclinical therapeutic trials.
Authors
Jasmine C. Wong, Pedro A. Perez-Mancera, Tannie Q. Huang, Jangkyung Kim, Joaquim Grego-Bessa, Maria del pilar Alzamora, Scott C. Kogan, Amnon Sharir, Susan H. Keefe, Carolina E. Morales, Denny Schanze, Pau Castel, Kentaro Hirose, Guo N. Huang, Martin Zenker, Dean Sheppard, Ophir Klein, David Tuveson, Benjamin S. Braun, Kevin Shannon
Schwannoma development is mediated by Hippo pathway dysregulation and modified by RAS/MAPK signaling
Abstract
Schwannomas are tumors of the Schwann cells that cause chronic pain, numbness, and potentially life-threatening impairment of vital organs. Despite the identification of causative genes including NF2 (Merlin), INI1/SMARCB1, and LZTR1, the exact molecular mechanism of schwannoma development is still poorly understood. Several studies have identified Merlin as a key regulator of the Hippo, MAPK, and PI3K signaling pathways, however definitive evidence demonstrating the importance of these pathways in schwannoma pathogenesis is absent. Here, we provide direct genetic evidence that dysregulation of the Hippo pathway in the Schwann cell lineage causes development of multiple Schwannomas in mice. We found that canonical Hippo signaling through the effectors YAP/TAZ is required for schwannomagenesis and that MAPK signaling modifies schwannoma formation. Furthermore, co-targeting YAP/TAZ transcriptional activity and MAPK signaling demonstrated a synergistic therapeutic effect on schwannoma. Our new model provides a tractable platform to dissect the molecular mechanisms underpinning schwannoma formation and the role of combinatorial targeted therapy in schwannoma treatment.
Authors
Zhiguo Chen, Stephen Li, Juan Mo, Eric T. Hawley, Yong Wang, Yongzheng He, Jean-Philippe Brosseau, Tracey Shipman, D. Wade Clapp, Thomas J. Carroll, Lu Q. Le
Abstract
ZIP8 is a metal transporter with a role in manganese (Mn) homeostasis. A common genetic variant in ZIP8 (rs13107325; A391T) ranks in the top 10 of pleiotropic single nucleotide polymorphisms (SNP) identified in genome-wide association studies, including associations with an increased risk of schizophrenia, obesity, Crohn’s disease, and reduced blood Mn. Here, we used CRISPR/Cas9-mediated knock-in (KI) to generate a mouse model of ZIP8 A391T (mouse Zip8 393T-KI). Recapitulating the SNP association with blood Mn, blood Mn is reduced in Zip8 393T-KI mice. There is restricted abnormal tissue Mn homeostasis with decreases in liver and kidney Mn and reciprocal increase in biliary Mn to provide in vivo evidence of hypomorphic Zip8 function. Upon challenge in a chemical-induced colitis model, male Zip8 393T-KI mice exhibited enhanced disease susceptibility. ZIP8 391-Thr associated with reduced triantennary plasma N-glycan species in a population-based cohort to define a genotype-specific glycophenotype hypothesized to be linked to Mn-dependent glycosyltransferase activity. This glycophenotype was maintained in a cohort of Crohn’s disease patients. These data and the pleiotropic disease associations with ZIP8 391-Thr suggest underappreciated roles of Mn homeostasis in compex human disease.
Authors
Laxmi Sunuwar, Azra Frkatovic, Sodbo Sharapov, Qinchuan Wang, Heather Neu, Xinqun Wu, Talin Haritunians, Fengyi Wan, Sarah L. J. Michel, Shaoguang Wu, Dermot McGovern, Gordan Lauc, Mark Donowitz, Cynthia L. Sears, Joanna M.P. Melia
Abstract
More than 90% of autoimmune-associated variants are located in noncoding regions, leading to challenges in deciphering the underlying causal roles of functional variants and genes and biological mechanisms. Therefore, to reduce the gap between traditional genetic findings and mechanistic understanding of disease etiologies and clinical drug development, it is important to translate systematically the regulatory mechanisms underlying noncoding variants. Here, we prioritized functional noncoding SNPs with regulatory gene targets associated with 19 autoimmune diseases by incorporating hundreds of immune cell–specific multiomics data. The prioritized SNPs are associated with transcription factor (TF) binding, histone modification, or chromatin accessibility, indicating their allele-specific regulatory roles. Their target genes are significantly enriched in immunologically related pathways and other known immunologically related functions. We found that 90.1% of target genes are regulated by distal SNPs involving several TFs (e.g., the DNA-binding protein CCCTC-binding factor [CTCF]), suggesting the importance of long-range chromatin interaction in autoimmune diseases. Moreover, we predicted potential drug targets for autoimmune diseases, including 2 genes (NFKB1 and SH2B3) with known drug indications on other diseases, highlighting their potential drug repurposing opportunities. Taken together, these findings may provide useful information for future experimental follow-up and drug applications on autoimmune diseases.
Authors
Xiao-Feng Chen, Ming-Rui Guo, Yuan-Yuan Duan, Feng Jiang, Hao Wu, Shan-Shan Dong, Xiao-Rong Zhou, Hlaing Nwe Thynn, Cong-Cong Liu, Lin Zhang, Yan Guo, Tie-Lin Yang
Abstract
Lynch syndrome is the most common colorectal cancer (CRC) hereditary form and it is characterized by DNA mismatch repair (MMR) deficiency. The term Lynch-like syndrome (LLS) is used for patients with MMR-deficient tumors and neither germline mutation in MLH1, MSH2, MSH6, PMS2, or EPCAM, nor MLH1 somatic methylation. Biallelic somatic inactivation or cryptic germline MMR variants undetected during genetic testing have been proposed to be involved. Sixteen patients with early-onset LLS CRC were selected for germline and tumor whole-exome sequencing. Two potentially pathogenic germline MCM8 variants were detected in a LLS male patient with fertility problems. A knockout cellular model for MCM8 was generated by CRISPR-Cas9 and detected genetic variants were produced by mutagenesis. DNA damage, microsatellite instability and mutational signatures were monitored. DNA damage was evident for MCM8KO cells and the analyzed genetic variants. Microsatellite instability and mutational signatures in MCM8KO cells were compatible with the involvement of MCM8 in MMR. Replication in an independent familial cancer cohort detected additional carriers. Unexplained MMR-deficient CRC cases, even showing somatic biallelic MMR inactivation, may be caused by underlying germline defects in genes different than the MMR genes. We suggest MCM8 as a new gene involved in CRC germline predisposition with a recessive pattern of inheritance.
Authors
Mariano Golubicki, Laia Bonjoch, José G. Acuña-Ochoa, Marcos Díaz-Gay, Jenifer Muñoz, Miriam Cuatrecasas, Teresa Ocaña, Soledad Iseas, Guillermo Mendez, Daniel Cisterna, Stephanie A. Schubert, Maartje Nielsen, Tom van Wezel, Yael Goldberg, Eli Pikarsky, Juan Robbio, Enrique Roca, Antoni Castells, Francesc Balaguer, Marina Antelo, Sergi Castellví-Bel
Abstract
Nexilin (NEXN) was recently identified as a component of the junctional membrane complex required for development and maintenance of cardiac T-tubules. Loss of Nexn in mice leads to a rapidly progressive dilated cardiomyopathy (DCM) and premature death. A 3 bp deletion (1948–1950del) leading to loss of the glycine in position 650 (G650del) is classified as a variant of uncertain significance in humans and may function as an intermediate risk allele. To determine the effect of the G650del variant on cardiac structure and function, we generated a G645del-knockin (G645del is equivalent to human G650del) mouse model. Homozygous G645del mice express about 30% of the Nexn expressed by WT controls and exhibited a progressive DCM characterized by reduced T-tubule formation, with disorganization of the transverse-axial tubular system. On the other hand, heterozygous Nexn global KO mice and genetically engineered mice encoding a truncated Nexn missing the first N-terminal actin-binding domain exhibited normal cardiac function, despite expressing only 50% and 20% of the Nexn, respectively, expressed by WT controls, suggesting that not only quantity but also quality of Nexn is necessary for a proper function. These findings demonstrated that Nexn G645 is crucial for Nexn’s function in tubular system organization and normal cardiac function.
Authors
Canzhao Liu, Simone Spinozzi, Wei Feng, Ze’e Chen, Lunfeng Zhang, Siting Zhu, Tongbin Wu, Xi Fang, Kunfu Ouyang, Sylvia M. Evans, Ju Chen
Abstract
Cancer is instigated by mutator phenotypes, including deficient mismatch repair and p53-associated chromosomal instability. More recently, a distinct class of cancers was identified with unusually high mutational loads due to heterozygous amino acid substitutions (most commonly P286R) in the proofreading domain of DNA polymerase ε, the leading strand replicase encoded by POLE. Immunotherapy has revolutionized cancer treatment, but new model systems are needed to recapitulate high mutational burdens characterizing human cancers and permit study of mechanisms underlying clinical responses. Here, we show that activation of a conditional LSL-PoleP286R allele in endometrium is sufficient to elicit in all animals endometrial cancers closely resembling their human counterparts, including very high mutational burden. Diverse investigations uncovered potentially novel aspects of Pole-driven tumorigenesis, including secondary p53 mutations associated with tetraploidy, and cooperation with defective mismatch repair through inactivation of Msh2. Most significantly, there were robust antitumor immune responses with increased T cell infiltrates, accelerated tumor growth following T cell depletion, and unfailing clinical regression following immune checkpoint therapy. This model predicts that human POLE-driven cancers will prove consistently responsive to immune checkpoint blockade. Furthermore, this is a robust and efficient approach to recapitulate in mice the high mutational burdens and immune responses characterizing human cancers.
Authors
Hao-Dong Li, Changzheng Lu, He Zhang, Qing Hu, Junqiu Zhang, Ileana C. Cuevas, Subhransu S. Sahoo, Mitzi Aguilar, Elizabeth G. Maurais, Shanrong Zhang, Xiaojing Wang, Esra A. Akbay, Guo-Min Li, Bo Li, Prasad Koduru, Peter Ly, Yang-Xin Fu, Diego H. Castrillon
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