title: Novel de novo SPOCK1 mutation in a proband with developmental delay, microcephaly and agenesis of corpus callosum.
abstract: Whole exome sequencing made it possible to identify novel de novo mutations in genes that might be linked to human syndromes (genotype first analysis). We describe a female patient with a novel de novo SPOCK1 variant, which has not been previously been associated with a human phenotype. Her features include intellectual disability with dyspraxia, dysarthria, partial agenesis of corpus callosum, prenatal-onset microcephaly and atrial septal defect with aberrant subclavian artery. Previous genetic, cytogenomic and metabolic studies were unrevealing. At age 13 years, exome sequencing on the patient and her parents revealed a de novo novel missense mutation in SPOCK1 (coding for Testican-1) on chromosome 5q31: c.239A>T (p.D80V). This mutation affects a highly evolutionarily conserved area of the gene, replacing a polar aspartic acid with hydrophobic nonpolar valine, and changing the chemical properties of the protein product, likely representing a pathogenic variant. Previous microdeletions of 5q31 including SPOCK1 have suggested genes on 5q31 as candidates for intellectual disability. No mutations or variants in other genes potentially linked to her phenotype were identified. Testicans are proteoglycans belonging to the BM-40/SPARC/osteonectin family of extracellular calcium-binding proteins. Testican-1 is encoded by the SPOCK1 gene, and mouse models have been shown it to be strongly expressed in the brain and to be involved in neurogenesis. We hypothesize that because this gene function is critical for neurogenesis, mutations could potentially lead to a phenotype with developmental delay and microcephaly.
authors.affiliation: Department of Medical Genetics, Mayo Clinic, Rochester, MN, USA.
authors.forename: Radhika
authors.initials: R
authors.lastname: Dhamija
authors.affiliation: Medical Genetics Institute, Cedars-Sinai Medical Center, Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Graham
authors.affiliation: GeneDx, Gaithersburg, MD, USA.
authors.forename: Nizar
authors.initials: N
authors.lastname: Smaoui
authors.affiliation: Departement of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Thorland
authors.affiliation: Department of Medical Genetics, Mayo Clinic, Rochester, MN, USA. Electronic address: kirmani.salman@mayo.edu.
authors.forename: Salman
authors.initials: S
authors.lastname: Kirmani
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D000293:Adolescent; D061085:Agenesis of Corpus Callosum / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods; D002658:Developmental Disabilities / Q000235:genetics*; D059472:Exome / Q000235:genetics; D005260:Female; D006801:Humans; D008831:Microcephaly / Q000235:genetics*; D020125:Mutation, Missense; D011509:Proteoglycans / Q000235:genetics*
chemical_list: D011509:Proteoglycans; C504369:SPOCK1 protein, human
keywords: Agenesis of corpus callosum; Developmental delay; Exome sequencing; Microcephaly; SPOCK1 mutation