Further clinical and molecular delineation of the 9q subtelomeric deletion syndrome supports a major contribution of EHMT1 haploinsufficiency to the core phenotype

Abstract

Further clinical and molecular delineation of the 9q subtelomeric deletion syndrome supports a major contribution of EHMT1 haploinsufficiency to the core phenotype Updated information and services can be found at: AbstractThe 9q Subtelomeric Deletion Syndrome (9qSTDS) is clinically characterized by moderate to severe mental retardation, childhood hypotonia and facial dysmorphisms. In addition, congenital heart defects, urogenital defects, epilepsy and behavioral problems are frequently observed. The syndrome can be either caused by a submicroscopic 9q34.3 deletion or by intragenic EHMT1 mutations leading to haploinsufficiency of the EHMT1 gene. So far it has not been established if and to what extent other genes in the 9q34.3 region contribute to the phenotype observed in deletion cases. Here we report the largest cohort of 9qSTDS cases so far. By a Multiplex Ligation dependent Probe Amplification approach, we identified and characterized 16 novel submicroscopic 9q deletions. Direct sequence analysis of the EHMT1 gene in 24 patients exhibiting the 9qSTD phenotype without such deletion, identified 6 patients with an intragenic EHMT1 mutation. Five of these mutations predict a premature termination codon whereas one mutation gives rise to an amino acid substitution in a conserved domain of the protein.Our data do not provide any evidence for phenotype-genotype correlations between size of the deletions or type of mutations and severity of clinical features. Therefore, we confirm the EHMT1 gene to be the major determinant of the 9qSTDS phenotype.

Adult Phenotypes in Angelman- and Rett-Like Syndromes

“…Adult patients with Kleefstra syndrome have rarely been reported before [Kleefstra et al, 2006[Kleefstra et al, , 2009Verhoeven et al, 2010Verhoeven et al, , 2011Willemsen et al, this issue]. Table 1 summarizes the phenotypic features of the present and 12 previously reported adult patients diagnosed with Kleefstra syndrome.…”

A mosaic maternal splice donor mutation in the EHMT1 gene leads to aberrant transcripts and to Kleefstra syndrome in the offspring

“…5 All EHMT1 point mutations described so far have appeared de novo in the patients. 6 Here, we report on a patient with characteristic features of Kleefstra syndrome carrying a novel splice-site mutation in EHMT1. The mutation was inherited from the mother who showed tissue-specific mosaicism.…”

MLL2 mutation spectrum in 45 patients with Kabuki syndrome

“…MLL2 is involved in regulation of cell adhesion, growth impairment and cell motility (Issaeva et al 2007). Interestingly, methyl transferase pathways in general have been implicated before in the pathology of MR syndromes such as Kleefstra Syndrome (MIM# 610253) which is caused by mutations in the EHMT1 gene, an H3K9 methyl transferase, and Schinzel-Giedion syndrome (MIM# 269150) which is caused by mutations in the SET1BP1 gene that encodes a protein known to bind to SET domains (Hoischen et al, 2010;Kleefstra, et al, 2009).…”