De Novo Missense Substitutions in the Gene Encoding CDK8, a Regulator of the Mediator Complex, Cause a Syndromic Developmental Disorder

The Mediator is an evolutionarily conserved, multi-subunit complex that regulates multiple steps of transcription. Mediator activity is regulated by the reversible association of a four-subunit module comprising CDK8 or CDK19 kinases, together with cyclin C, MED12 or MED12L, and MED13 or MED13L. Mutations in MED12, MED13, and MED13L were previously identified in syndromic developmental disorders with overlapping phenotypes. Here, we report CDK8 mutations (located at 13q12.13) that cause a phenotypically related disorder. Using whole-exome or whole-genome sequencing, and by international collaboration, we identified eight different heterozygous missense CDK8 substitutions, including 10 shown to have arisen de novo, in 12 unrelated subjects; a recurrent mutation, c.185C>T (p.Ser62Leu), was present in five individuals. All predicted substitutions localize to the ATP-binding pocket of the kinase domain. Affected individuals have overlapping phenotypes characterized by hypotonia, mild to moderate intellectual disability, behavioral disorders, and variable facial dysmorphism. Congenital heart disease occurred in six subjects; additional features present in multiple individuals included agenesis of the corpus callosum, ano-rectal malformations, seizures, and hearing or visual impairments. To evaluate the functional impact of the mutations, we measured phosphorylation at STAT1-Ser727, a known CDK8 substrate, in a CDK8 and CDK19 CRISPR double-knockout cell line transfected with wild-type (WT) or mutant CDK8 constructs. These experiments demonstrated a reduction in STAT1 phosphorylation by all mutants, in most cases to a similar extent as in a kinase-dead control. We conclude that missense mutations in CDK8 cause a developmental disorder that has phenotypic similarity to syndromes associated with mutations in other subunits of the Mediator kinase module, indicating probable overlap in pathogenic mechanisms

The phenotype of Floating-Harbor syndrome in 10 patients.

Floating-Harbor syndrome (FHS) is a rare condition typified by short stature, speech impairment, delayed bone age, and characteristic facies. The diagnosis can be difficult as the facial changes are subtle in infancy, and the features of short stature, delayed speech, and delayed bone age are frequently encountered in clinical practice. We refine the phenotype in FHS by reporting clinical findings in 10 typically affected individuals ranging in age from 7 to 34 years and present a mother and daughter who display some features of FHS. Bone age measurements were delayed when measured from age 6 months to 6 years but in some patients were normal between 6 and 12 years. Dysmorphic features at different ages are characterized. The lateral profile of the face and the characteristic body habitus aided diagnosis. Significant behavioral problems of hyperactivity, short attention span and aggression during childhood were reported for most individuals. The children studied had a severe and incapacitating disorder of speech and language. Intellectual functioning ranged from borderline normal to moderate intellectual disability. Early puberty was noted. Adult heights were 140-155 cm. Microarray analysis in eight of the patients provided no evidence that FHS is caused by a large-scale copy-number genomic change

Form of autosomal dominant spondyloepiphyseal dysplasia is caused by a glycine to alanine substitution in the COL2A1 gene

Form of autosomal dominant spondyloepiphyseal dysplasia is caused by a glycine to alanine substitution in the COL2A1 gene We report a family with an unusual form of autosomal dominant spondyloepiphyseal dysplasia characterized by infantile-onset disproportionate short stature with relative shortening of the spine, thoracic kyphosis, lumbar lordosis, scoliosis and premature osteoarthritis of the joints especially of the hips. Radiological findings include mild platyspondyly, vertebral end plate irregularity, irregular femoral necks, and dysplasia of the capital femoral epiphyses with flattening and irregularity present from childhood and mild variable epiphyseal dysplasia elsewhere in the skeleton. Intrafamilial variability is observed in the degree of short stature, severity of spinal and hip involvement and the age of onset of symptoms and complications. We demonstrate that this dysplasia is due to a glycine to alanine substitution in the COL2A1 gene (p.Gly862Ala), thereby expanding the phenotypic spectrum of dysplasias associated with defects in type II collagen