Search

Primrose syndrome (PS) is a rare disorder characterized by macrocephaly, tall stature, intellectual disability, autistic traits, and disturbances of glucose metabolism with insulin-resistant diabetes and distal muscle wasting occurring in adulthood. The disorder is caused by functional dysregulation of ZBTB20, a transcriptional repressor controlling energetic metabolism and developmental programs. ZBTB20 maps in a genomic region that is deleted in the 3q13.31 microdeletion syndrome, which explains the clinical overlap between the two disorders. A narrow spectrum of amino acid substitutions in a restricted region of ZBTB20 encompassing the first and second zinc-finger motifs have been reported thus far. Here, we characterize clinically and functionally the first truncating mutation [(c.1024delC; p.(Gln342Serfs*42)] and a missense change affecting the third zinc-finger motif of the protein [(c.1931C > T; p.(Thr644Ile)]. Our data document that both mutations have dominant negative impact on wild-type ZBTB20, providing further evidence of the specific behavior of PS-causing mutations on ZBTB20 function., (© 2018 Wiley Periodicals, Inc.)

The etiology of mental retardation remains elusive in the majority of cases. Microdeletions within chromosomal bands 5q14.3q15 were recently identified as a recurrent cause of severe mental retardation, epilepsy, muscular hypotonia, and variable minor anomalies. By molecular karyotyping we identified two novel 2.4- and 1.5-Mb microdeletions of this region in patients with a similar phenotype. Both deletions contained the MEF2C gene, which is located proximally to the previously defined smallest region of overlap. Nevertheless, due to its known role in neurogenesis, we considered MEF2C as a phenocritical candidate gene for the 5q14.3q15 microdeletion phenotype. We therefore performed mutational analysis in 362 patients with severe mental retardation and found two truncating and two missense de novo mutations in MEF2C, establishing defects in this transcription factor as a novel relatively frequent autosomal dominant cause of severe mental retardation accounting for as much as 1.1% of patients. In these patients we found diminished MECP2 and CDKL5 expression in vivo, and transcriptional reporter assays indicated that MEF2C mutations diminish synergistic transactivation of E-box promoters including that of MECP2 and CDKL5. We therefore conclude that the phenotypic overlap of patients with MEF2C mutations and atypical Rett syndrome is due to the involvement of a common pathway.