A fourteen years follow-up of a case of partial trisomy 12q and monosomy 12p recombinants of a familial pericentric inversion of chromosome 12: Clinical, cytogenetic and molecular observations

Familial Congenital Facial Synkinesis Due to 12q Duplication: A Case Report and Literature Review

Inverse Marcus Gunn phenomenon is a rare form of congenital facial synkinesis in which jaw movement temporarily elicits ptosis, either unilateral or bilateral. This phenomenon is presumed to result from dysinnervation of facial muscles during development of the nervous system. We describe 2 brothers, both with inverse Marcus Gunn phenomenon in the context of multiple other congenital anomalies, all presumed secondary to a chromosomal abnormality involving 12q duplication and 1p36 deletion. Although a handful of familial cases of congenital facial synkinesis have been previously described, this is the first in which a genetic abnormality has been identified. Of the 4 genetic abnormalities previously described in association with congenital facial synkinesis (based on isolated case reports), 1 also involved duplication at the long arm of chromosome 12. We conclude that duplication of ≥1 of the roughly 44 protein-coding genes in the ∼6.3-Mb overlap region between the previously published case and our 2 patients is a likely genetic cause of congenital facial synkinesis.

A locus on mouse Ch10 influences susceptibility to limbic seizure severity: fine mapping and in silico candidate gene analysis

Identification of genes contributing to mouse seizure susceptibility can reveal novel genes or pathways that provide insight into human epilepsy. Using mouse chromosome substitution strains and interval-specific congenic strains (ISCS), we previously identified an interval conferring pilocarpine-induced limbic seizure susceptibility on distal mouse chromosome 10 (Ch10). We narrowed the region by generating subcongenics with smaller A/J Ch10 segments on a C57BL/6J (B6) background and tested them with pilocarpine. We also tested pilocarpine-susceptible congenics for 6-Hz ECT (electroconvulsive threshold), another model of limbic seizure susceptibility, to determine whether the susceptibility locus might have a broad effect on neuronal hyperexcitability across more than one mode of limbic seizure induction. The ISCS Line 1, which contained the distal 2.7 Mb segment from A/J (starting at rs29382217), was more susceptible to both pilocarpine and ECT. Line 2, which was a subcongenic of Line 1 (starting at rs13480828), was not susceptible, thus defining a 1.0 Mb critical region that was unique to Line 1. Bioinformatic approaches identified 45 human orthologs within the unique Line 1 susceptibility region, the majority syntenic to human Ch12. Applying an epilepsy network analysis of known and suspected excitability genes and examination of interstrain genomic and brain expression differences revealed novel candidates within the region. These include Stat2, which plays a role in hippocampal GABA receptor expression after status epilepticus, and novel candidates Pan2, Cdk2, Gls2 and Cs, which are involved in neural cell differentiation, cellular remodeling and embryonic development. Our strategy may facilitate discovery of novel human epilepsy genes.

A new partial trisomy 12p with artery catheter vagus, congenital cataracts, external auditory canal, and no turbinate

We describe the prenatal diagnosis and fetal phenotype of partial trisomy 12 (p12-pter) transmitted from a maternal reciprocal translocation 6;12. Genetic analysis was conducted on umbilical cord blood for a fetus accompanied with tricuspid regurgitation and orbital hypertelorism from a 27-year-old gravida 4, para 1 after sonography at gestation 35 weeks. The karyotype was unusual, with 46, XY, der (6), t (6;12) (p24; p12) mat. The pregnancy was terminated at 37 gestational weeks. The aborted fetus displayed dysmorphic features of a round flat face with prominent cheeks and high forehead, hypertelorism, short nose, broad and depressed nasal bridge, anteverted nares, deformed philtrum, open mouth, thin upper vermilion and broad everted lower lip, low-set ears and aural atresia, broad hands with simian creases, and a short neck. Fetal anatomy showed right artery catheter vagus, congenital cataract, no turbinate and external auditory canals. Through karyotype-phenotype analysis of this patient and a review of other reported cases, we believe this is a first report that expands the database of partial trisomy 12p, and is beneficial for future clinical genetic counseling. This study supports that phenotypic variability depends on the type and extent of the associated partial monosomy.