A novel missense variant in the CASK gene causes intellectual developmental disorder and microcephaly with pontine and cerebellar hypoplasia. 2022

Sixian Wu, and Chuan Jiang, and Jiaman Li, and Guohui Zhang, and Ying Shen, and Jing Wang
Joint Laboratory of Reproductive Medicine, Gynaecology and Paediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, 610041, People's Republic of China.

Variants in the CASK gene result in a wide range of observed phenotypes in humans, such as FG Syndrome 4 and intellectual disabilities. Intellectual developmental disorder with microcephaly and pontine and cerebellar hypoplasia (MICPCH) is an X-linked disorder that affects females and is characterized by severely impaired intellectual development and variable degrees of pontocerebellar hypoplasia. Variants in CASK are the main genetic cause of MICPCH. Variants in CASK can explain most patients with MICPCH, but there are still some patients whose disease aetiology cannot be explained. An 11-month-old female diagnosed with MICPCH exhibited general developmental delays, microcephaly, and cerebellar hypoplasia. Whole-exome sequencing (WES) was used to find a novel heterozygous missense variant (NM_003688.3: c.638T>G) of CASK in this patient. Strikingly, this variant reduced the expression of CASK at the protein level but not at the mRNA level. By using protein structure prediction analysis, this study found that the amino acid change caused by the variant resulted in further changes in the stability of the protein structure, and these changes caused the downregulation of protein expression and loss of protein function. In this study, we first reported a novel heterozygous pathogenic variant and a causative mechanism of MICPCH. The amino acid change cause by this variant led to changes in the protein structure and a decrease in its stability, which caused a loss of protein function. This study could be helpful to the genetic diagnosis of this disease.

UI MeSH Term Description Entries
D007223 Infant A child between 1 and 23 months of age. Infants
D008607 Intellectual Disability Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual has an intellectual disability. IQ scores between 70 and 79 are in the borderline range. Scores below 67 are in the disabled range. (from Joynt, Clinical Neurology, 1992, Ch55, p28) Disability, Intellectual,Idiocy,Mental Retardation,Retardation, Mental,Deficiency, Mental,Intellectual Development Disorder,Mental Deficiency,Mental Retardation, Psychosocial,Deficiencies, Mental,Development Disorder, Intellectual,Development Disorders, Intellectual,Disabilities, Intellectual,Disorder, Intellectual Development,Disorders, Intellectual Development,Intellectual Development Disorders,Intellectual Disabilities,Mental Deficiencies,Mental Retardations, Psychosocial,Psychosocial Mental Retardation,Psychosocial Mental Retardations,Retardation, Psychosocial Mental,Retardations, Psychosocial Mental
D008831 Microcephaly A congenital abnormality in which the CEREBRUM is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (Desk Reference for Neuroscience, 2nd ed.) Microlissencephaly,Severe Congenital Microcephaly,Congenital Microcephalies, Severe,Congenital Microcephaly, Severe,Microcephalies,Microcephalies, Severe Congenital,Microcephaly, Severe Congenital,Microlissencephalies,Severe Congenital Microcephalies
D009421 Nervous System Malformations Structural abnormalities of the central or peripheral nervous system resulting primarily from defects of embryogenesis. Nervous System Abnormalities,Abnormalities, Congenital, Nervous System,Abnormalities, Nervous System,Anomalies, Nervous System,Congenital Abnormalities, Nervous System,Congenital Anomalies, Nervous System,Congenital Malformations, Nervous System,Cranioschisis,Malformations, Nervous System, Congenital,Nervous System Anomalies,Nervous System Congenital Abnormalities,Nervous System Congenital Malformations,Nervous System Malformations, Congenital,Abnormality, Nervous System,Anomaly, Nervous System,Cranioschises,Malformation, Nervous System,Malformations, Nervous System,Nervous System Abnormality,Nervous System Anomaly,Nervous System Malformation
D010641 Phenotype The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment. Phenotypes
D002531 Cerebellum The part of brain that lies behind the BRAIN STEM in the posterior base of skull (CRANIAL FOSSA, POSTERIOR). It is also known as the "little brain" with convolutions similar to those of CEREBRAL CORTEX, inner white matter, and deep cerebellar nuclei. Its function is to coordinate voluntary movements, maintain balance, and learn motor skills. Cerebella,Corpus Cerebelli,Parencephalon,Cerebellums,Parencephalons
D002658 Developmental Disabilities Disorders in which there is a delay in development based on that expected for a given age level or stage of development. These impairments or disabilities originate before age 18, may be expected to continue indefinitely, and constitute a substantial impairment. Biological and nonbiological factors are involved in these disorders. (From American Psychiatric Glossary, 6th ed) Child Development Deviations,Child Development Disorders,Child Development Disorders, Specific,Developmental Delay Disorders,Disabilities, Developmental,Development Disorders, Child,Child Development Deviation,Child Development Disorder,Development Deviation, Child,Development Deviations, Child,Development Disorder, Child,Developmental Delay Disorder,Developmental Disability,Deviation, Child Development,Disability, Developmental
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000596 Amino Acids Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins. Amino Acid,Acid, Amino,Acids, Amino

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