Ablepharon macrostomia syndrome (AMS) and Barber-Say syndrome (BSS) are rare congenital ectodermal dysplasias characterized by similar clinical features. To establish the genetic basis of AMS and BSS, we performed extensive clinical phenotyping, whole exome and candidate gene sequencing, and functional validations. We identified a recurrent de novo mutation in TWIST2 in seven independent AMS-affected families, as well as another recurrent de novo mutation affecting the same amino acid in ten independent BSS-affected families. Moreover, a genotype-phenotype correlation was observed, because the two syndromes differed based solely upon the nature of the substituting amino acid: a lysine at TWIST2 residue 75 resulted in AMS, whereas a glutamine or alanine yielded BSS. TWIST2 encodes a basic helix-loop-helix transcription factor that regulates the development of mesenchymal tissues. All identified mutations fell in the basic domain of TWIST2 and altered the DNA-binding pattern of Flag-TWIST2 in HeLa cells. Comparison of wild-type and mutant TWIST2 expressed in zebrafish identified abnormal developmental phenotypes and widespread transcriptome changes. Our results suggest that autosomal-dominant TWIST2 mutations cause AMS or BSS by inducing protean effects on the transcription factor's DNA binding.

Ablepharon-macrostomia syndrome (AMS) is characterized by absent or short eyelids, macrostomia, ear anomalies, absent lanugo and hair, redundant skin, abnormal genitalia, and developmental delay in two-thirds of the reported patients. Additional anomalies include dry skin, growth retardation, hearing loss, camptodactyly, hypertelorism, absent zygomatic arches, and umbilical abnormalities. We present the second familial case of ablepharon-macrostomia syndrome in a newborn female and her 22-year-old father making autosomal dominant inheritance more likely than the previously proposed autosomal recessive transmission for this disorder. These cases likely represent the 16th and 17th reported cases of AMS and the first case suspected on prenatal ultrasound. Additionally, the child shows more prominent features of the disorder when compared to her father documenting variable expression and possible anticipation.

Microarray analysis allows the screening of thousands of identifiable genes in a single experiment. The challenge of this approach is to combine the new technology with established genetic tools to associate genes with specific biological function. In this study we have designed a screen to identify imprinted genes from mice with uniparental duplications of proximal Chromosomes (Chrs) 7 and 11, using microarray analysis. By comparing the expression patterns in embryonic and newborn tissues of maternally versus paternally inherited proximal Chrs 7 and 11, we have correctly identified four out of five known imprinted genes represented on a microarray. We have additionally identified two novel imprinted candidate genes as well as a differentially expressed clone that is a potential downstream target. Interpretation of the microarray data requires careful preparation of age- and strain-matched samples and attention to detail in tissue dissection technique.