Phenotypic spectrum and extent of DNA methylation defects associated with multilocus imprinting disturbances

AIM

To characterize the genotypic and phenotypic extent of multilocus imprinting disturbances (MLID).

MATERIALS & METHODS

We analyzed 37 patients with imprinting disorders (explorative cohort) for DNA methylation changes using the Infinium HumanMethylation450 BeadChip. For validation, three independent cohorts with imprinting disorders or cardinal features thereof were analyzed (84 patients with imprinting disorders, 52 with growth disorder, 81 with developmental delay).

RESULTS

In the explorative cohort 21 individuals showed array-based MLID with each one displaying an Angelman or Temple syndrome phenotype, respectively. Epimutations in ZDBF2 and FAM50B were associated with severe MLID regarding number of affected regions. By targeted analysis we identified methylation changes of ZDBF2 and FAM50B also in the three validation cohorts.

CONCLUSION

We corroborate epimutations in ZDBF2 and FAM50B as frequent changes in MLID whereas these rarely occur in other patients with cardinal features of imprinting disorders. Moreover, we show cell lineage specific differences in the genomic extent of FAM50B epimutation.

Exome sequencing identifies a de novo frameshift mutation in the imprinted gene ZDBF2 in a sporadic patient with Nasopalpebral Lipoma-coloboma syndrome

Nasopalpebral lipoma-coloboma syndrome (NPLCS, OMIM%167730) is an uncommon malformation entity with autosomal dominant inheritance characterized by the combination of nasopalpebral lipoma, colobomas in upper and lower eyelids, telecanthus, and maxillary hypoplasia. To date, no genetic defects have been associated with familial or sporadic NPLCS cases and the etiology of the disease remains unknown. In this work, the results of whole exome sequencing in a sporadic NPLCS patient are presented. Exome sequencing identified a de novo heterozygous frameshift dinucleotide insertion c.6245_6246 insTT (p.His2082fs*67) in ZDBF2 (zinc finger, DBF-type containing 2), a gene located at 2q33.3. This variant was absent in parental DNA, in a set of 300 ethnically matched controls, and in public exome variant databases. This is the first genetic variant identified in a NPLCS patient and evidence supporting the pathogenicity of the identified mutation is discussed. © 2016 Wiley Periodicals, Inc.