Heterozygous pathogenic variants in POLR1A, which encodes the largest subunit of RNA Polymerase I, were previously identified as the cause of acrofacial dysostosis, Cincinnati-type. The predominant phenotypes observed in the cohort of 3 individuals were craniofacial anomalies reminiscent of Treacher Collins syndrome. We subsequently identified 17 additional individuals with 12 unique heterozygous variants in POLR1A and observed numerous additional phenotypes including neurodevelopmental abnormalities and structural cardiac defects, in combination with highly prevalent craniofacial anomalies and variable limb defects. To understand the pathogenesis of this pleiotropy, we modeled an allelic series of POLR1A variants in vitro and in vivo. In vitro assessments demonstrate variable effects of individual pathogenic variants on ribosomal RNA synthesis and nucleolar morphology, which supports the possibility of variant-specific phenotypic effects in affected individuals. To further explore variant-specific effects in vivo, we used CRISPR-Cas9 gene editing to recapitulate two human variants in mice. Additionally, spatiotemporal requirements for Polr1a in developmental lineages contributing to congenital anomalies in affected individuals were examined via conditional mutagenesis in neural crest cells (face and heart), the second heart field (cardiac outflow tract and right ventricle), and forebrain precursors in mice. Consistent with its ubiquitous role in the essential function of ribosome biogenesis, we observed that loss of Polr1a in any of these lineages causes cell-autonomous apoptosis resulting in embryonic malformations. Altogether, our work greatly expands the phenotype of human POLR1A-related disorders and demonstrates variant-specific effects that provide insights into the underlying pathogenesis of ribosomopathies.
- MeSH
- apoptóza MeSH
- crista neuralis patologie MeSH
- fenotyp MeSH
- kraniofaciální abnormality * genetika patologie MeSH
- lidé MeSH
- mandibulofaciální dysostóza * genetika MeSH
- mutageneze MeSH
- myši MeSH
- ribozomy genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Activating germline RET mutations are presented in patients with familial medullary thyroid carcinoma (FMTC) and multiple endocrine neoplasia (MEN) types 2A and 2B, whereas inactivating germline mutations in patients with Hirschsprung's disease (HSCR). The aim of this study was to evaluate genotype-phenotype correlations of the frequently discussed Tyr791Phe mutation in exon 13 of the RET proto-oncogene. Screening of three groups of patients was performed (276 families with medullary thyroid carcinoma (MTC), 122 families with HSCR, and 29 patients with pheochromocytoma). We found this mutation in 3 families with apparently sporadic MTC, 3 families with FMTC/MEN2, 1 patient with pheochromocytoma, and 3 families with HSCR. All gene mutation carriers have a silent polymorphism Leu769Leu in exon 13. In three families second germline mutations were detected: Cys620Phe (exon 10) in MEN2A family, Met918Thr (exon 16) in MEN2B family, and Ser649Leu (exon 11) in HSCR patient. Detection of the Tyr791Phe mutation in MEN2/MTC and also in HSCR families leads to the question whether this mutation has a dual character (gain-of-function as well as loss-of-function). A rare case of malignant pheochromocytoma in a patient with the Tyr791Phe mutation is presented. This study shows various clinical characteristics of the frequently discussed Tyr791Phe mutation.
- MeSH
- crista neuralis patologie MeSH
- dítě MeSH
- dospělí MeSH
- fenylalanin genetika MeSH
- genetické asociační studie MeSH
- Hirschsprungova nemoc genetika MeSH
- jednonukleotidový polymorfismus fyziologie MeSH
- lidé středního věku MeSH
- lidé MeSH
- medulární karcinom genetika MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mnohočetná endokrinní neoplazie typ 2A genetika MeSH
- nádory štítné žlázy genetika MeSH
- nemoc genetika MeSH
- protoonkogenní proteiny c-ret genetika MeSH
- rodina MeSH
- senioři MeSH
- substituce aminokyselin genetika MeSH
- tyrosin genetika MeSH
- zárodečné mutace MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- kazuistiky MeSH
- práce podpořená grantem MeSH
Tumors that originate from neural crest-derived cells represent a heterogeneous group of neoplasms including benign and malignant tumors with melanocytic and schwannian differentiation. The immunophenotype of these tumors is well known but little is known about the expression of smooth muscle/myofibroblastic markers in these tumors. A total of 590 neural crest-derived tumors (50 benign schwannomas, five malignant peripheral nerve sheath tumors, 80 neurofibromas, 240 nevocytic nevi, 115 primary melanomas, and 100 melanoma metastases) were studied with respect to alpha-smooth muscle actin and muscle-specific actin expression. alpha-Smooth muscle actin and muscle-specific actin-positive tumor cells with a co-expression of S-100 protein were found in one benign schwannoma, one primary cutaneous melanoma, and four melanoma metastases. Four of these cases were examined ultrastructurally, but typical actin filaments with focal densities were not found in any of the four. Other immunohistochemical markers examined including desmin, h-caldesmon and smooth muscle myosin heavy chain were negative in the tumor cells. The present results suggest that neural crest-derived tumors could show expression of alpha-smooth muscle actin on rare occasion.
- MeSH
- aktiny metabolismus ultrastruktura MeSH
- crista neuralis metabolismus patologie MeSH
- financování organizované MeSH
- lidé MeSH
- melanocyty metabolismus patologie MeSH
- melanom metabolismus sekundární MeSH
- nádorové biomarkery metabolismus MeSH
- nádory nervové pochvy metabolismus patologie MeSH
- neurilemom metabolismus patologie MeSH
- neurofibrom metabolismus patologie MeSH
- pigmentový névus metabolismus patologie MeSH
- Check Tag
- lidé MeSH
- MeSH
- crista neuralis patologie MeSH
- diferenciální diagnóza MeSH
- lidé MeSH
- nádory mozku patologie MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
