High mutation detection rates in cerebral cavernous malformation upon stringent inclusion criteria: one-third of probands are minors.

Cerebral cavernous malformations (CCM) are prevalent vascular malformations occurring in familial autosomal dominantly inherited or isolated forms. Once CCM are diagnosed by magnetic resonance imaging, the indication for genetic testing requires either a positive family history of cavernous lesions or clinical symptoms such as chronic headaches, epilepsy, neurological deficits, and hemorrhagic stroke or the occurrence of multiple lesions in an isolated case. Following these inclusion criteria, the mutation detection rates in a consecutive series of 105 probands were 87% for familial and 57% for isolated cases. Thirty-one novel mutations were identified with a slight shift towards proportionally more CCM3 mutations carriers than previously published (CCM1: 60%, CCM2: 18%, CCM3: 22%). In-frame deletions and exonic missense variants requiring functional analyses to establish their pathogenicity were rare: An in-frame deletion within the C-terminal FERM domain of CCM1 resulted in decreased protein expression and impaired binding to the transmembrane protein heart of glass (HEG1). Notably, 20% of index cases carrying a CCM mutation were below age 10 and 33% below age 18 when referred for genetic testing. Since fulminant disease courses during the first years of life were observed in CCM1 and CCM3 mutation carriers, predictive testing of minor siblings became an issue.

SALL1 mutations in sporadic Townes-Brocks syndrome are of predominantly paternal origin without obvious paternal age effect.

Autosomal dominant Townes-Brocks syndrome (TBS) is characterized by imperforate anus, triphalangeal and supernumerary thumbs, dysplastic ears and sensorineural hearing loss, and may also involve other organ systems. Strong inter- and intrafamiliar variability is known. Approximately 50% of TBS cases are sporadic and due to de novo mutations in the SALL1 gene. SALL1 encodes a zinc finger protein operating as a transcriptional repressor and localizing to pericentromeric heterochromatin. We traced the parental origin of SALL1 mutations in sporadic TBS by analysis of linkage between SALL1 mutations and exonic or intronic polymorphisms in 16 families with 10 different mutations. Mutations were of paternal origin in 14 of 16 cases (87.5%). Paternal origin was independent of the mutation type. The mean paternal age at conception was 29.9 and the mean maternal age 26.5 years. We conclude that de novo mutations in SALL1 mostly occur on the paternally derived chromosome 16 without an obvious age effect.