We had previously sequenced the exomes of individuals from four families, where at least one member was affected with MBS. We identified a few candidate genes (1-3) per family that had variants segregating with MBS (i.e. in affected family members and not in the non-affecteds). Notably, we had not identified candidate genes in common across two or more of the four families studied. Thus, it became clear that interrogating more homogeneous subgroups of affected individuals based on detailed clinical phenotyping was required given the complexity and heterogeneity of this disorder to identify common genetic and potential environmental factors. In light of this, we established a new NHGRI protocol in 2014 (14-HG-0055, ClinicalTrials.gov ID: NCT02055248; PI: Irini Manoli) dedicated to defining the phenotypes and the genetic factors associated with Moebius syndrome and other congenital facial weakness disorders. This protocol has been partially funded by a competitive UO1 grant awarded in January 2014, 1U01HD079068-03 (coPIs: Jabs, Engle, Manoli, Brooks, Pierpaoli) and a 2-year research grant from the Moebius Syndrome Foundation, awarded in January 2017. Initially, our goal was to enroll 24 participants and their family members each year, for 3 years, from 2014 to 2016. Since the beginning of 2017, our goal has been to enroll 10-12 participants per year, based on the funding from the Moebius Syndrome Foundation. As part of the protocol, the affected individual(s) from each family undergoes standardized multisystem phenotyping at the NIH Clinical Research Center (NIH CC). Specialists in ophthalmology, neurology, audiology, otolaryngology, dentistry, craniofacial surgery, speech pathology and rehabilitation medicine evaluate the study participants, providing deep phenotyping data for each specialty. To date, we have enrolled 64 patients and 79 family members as well as 18 healthy controls for brain imaging data analysis, for a total of 163 subjects. To date, 124/163 participants have visited the NIH CC for full clinical evaluation. Up until the end of 2016, we prioritized families with more than one affected individual, since we believed these would provide a better chance of identifying a causative germline mutation. Under the collaborative agreement between NIH, MSSM and BCH, each of the three teams in the UO1 grant (NIH: Manoli/Brooks/Pierpaoli; MSSM Jabs; BCH: Engle) analyzes the clinical and genetic data. To facilitate this, we have created a database to enable sharing of the clinical phenotype information. The detailed phenotype information has already allowed us to categorize the affected individuals into more clearly defined subgroups or categories, which will help inform and direct the genomic analyses that are currently in progress. The genomic data generated at the NIH is analyzed by all of the collaborating groups using various strategies, and variants are screened in the cohorts collected by our collaborators at MSSM and BCH. We have analysed whole exome sequence data from 111 individuals (54 affected and 57 unaffected) and have identified 131 variants in 44 genes that occurred in probands and/or segregated in affected members in two or more families. Furthermore, the Gabriella Miller Kids First Pediatric Research Program awarded resouces (Dr. Engle, BCH; X01HL132377) for whole genome sequencing at the Baylor Sequencing Core of 200 individuals and their family members with MBS or hereditary congenital facial paresis (HCFP). Data generated by this funding are being analyzed in collaboration with Daniel MacArthur at the Broad Institute. Our preliminary analyses have identified variations in a genomic region that is common to several families that meet a specific subset of diagnostic criteria and we are currently investigating this region further. We also assessed four individuals with Carey-Fineman-Ziter syndrome enrolled through John Carey (University of Utah) and Elizabeth Engle (BCH). Candidate mutations had been previously identified (by Drs Carey and Engle) in a gene (MYMK) that was common to all four individuals. In collaboration with Stephen Robertson (University of Otago, New Zealand) and Eric Olson (University of Texas Southwestern) we assessed and confirmed the functional relevance of these mutations in human myoblasts and the zebrafish model system. A manuscript describing the MYMK results was pubished at Nature Communications (1). Additionally, we have identified compound heterozygous mutations in STAC3, the gene causing Native-American myopathy, in two non-Native American siblings with a CFZS-like phenotype (2). We have autopsy material of an individual with classic Moebius syndrome. Postmortem brain imaging and high-resolution DTI reveals aberrant cranial nerve trajectory and highlights the utility of ex vivo micro-imaging approaches for describing abnormal neuroanatomy in human disorders, which is critical to understanding the pathophysiology of cranial nerve abnormalities in MBS. We have performed whole exome sequencing with lymphocyte DNA from this individual, in combination with whole genome sequencing of affected brainstem region (CNVII/VI nuclei) to identify somatic mutations. We believe this collaborative approach of bringing together expert investigators from multiple sites to combine valuable resources/data, will maximize our capacity to identify germline or somatic genetic causes of the various syndromes associated with facial palsy. Moreover, this collaboration has allowed the generation of a patient registry/clinical database in REDCap, as well as rich phenotypic and genotypic data that will be deposited in dbGap (Accession ID phs001383.v1.p1.) for further exploration by other investigators interested in conditions involving facial palsy.
| Telegrafi, Aida; Webb, Bryn D; Robbins, Sarah M et al. (2017) Identification of STAC3 variants in non-Native American families with overlapping features of Carey-Fineman-Ziter syndrome and Moebius syndrome. Am J Med Genet A 173:2763-2771 |
| Di Gioia, Silvio Alessandro; Connors, Samantha; Matsunami, Norisada et al. (2017) A defect in myoblast fusion underlies Carey-Fineman-Ziter syndrome. Nat Commun 8:16077 |
