Mutations in genes encoding subunits of RNA polymerases I and III cause Treacher Collins syndrome.

Center for Human and Clinical Genetics, Leiden University Medical Center (LUMC), Leiden, The Netherlands.
Nature Genetics (Impact Factor: 29.65). 01/2011; 43(1):20-2. DOI: 10.1038/ng.724
Source: PubMed

ABSTRACT We identified a deletion of a gene encoding a subunit of RNA polymerases I and III, POLR1D, in an individual with Treacher Collins syndrome (TCS). Subsequently, we detected 20 additional heterozygous mutations of POLR1D in 252 individuals with TCS. Furthermore, we discovered mutations in both alleles of POLR1C in three individuals with TCS. These findings identify two additional genes involved in TCS, confirm the genetic heterogeneity of TCS and support the hypothesis that TCS is a ribosomopathy.

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    ABSTRACT: Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA polymerases I and III (abbreviated as Pol I and Pol III), the first analysis of their physical compositions in plants. In all eukaryotes examined to date, AC40 and AC19 subunits are common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes. Surprisingly, A. thaliana and related species express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Pol III. Changes at eight amino acid positions correlate with the functional divergence of Pol I- and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit and either protein can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the 12 subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.
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    ABSTRACT: The production of ribosomes is ubiquitous and fundamental to life. As such, it is surprising that defects in ribosome biogenesis underlie a growing number of symptomatically distinct inherited disorders, collectively called ribosomopathies. We previously determined that the nucleolar protein, NOL11, is essential for optimal pre-rRNA transcription and processing in human tissue culture cells. However, the role of NOL11 in the development of a multicellular organism remains unknown. Here, we reveal a critical function for NOL11 in vertebrate ribosome biogenesis and craniofacial development. Nol11 is strongly expressed in the developing cranial neural crest (CNC) of both amphibians and mammals, and knockdown of Xenopus nol11 results in impaired pre-rRNA transcription and processing, increased apoptosis, and abnormal development of the craniofacial cartilages. Inhibition of p53 rescues this skeletal phenotype, but not the underlying ribosome biogenesis defect, demonstrating an evolutionarily conserved control mechanism through which ribosome-impaired craniofacial cells are removed. Excessive activation of this mechanism impairs craniofacial development. Together, our findings reveal a novel requirement for Nol11 in craniofacial development, present the first frog model of a ribosomopathy, and provide further insight into the clinically important relationship between specific ribosome biogenesis proteins and craniofacial cell survival.
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    ABSTRACT: Treacher Collins syndrome is an autosomal dominant disorder resulting in congenital craniofacial deformities. Scoliosis has not been previously reported as one of the extracranial manifestations of this syndromic condition. We present a 15-year-old British Caucasian girl with Treacher Collins syndrome who developed a severe double thoracic scoliosis measuring 102[degree sign] and 63[degree sign] respectively. The deformity was noted at age 14 years by the local general practitioner and gradually progressed until she was referred to our service and subsequently was scheduled for surgical correction. There were no congenital vertebral anomalies. As part of the condition, she had bilateral conductive hearing impairment. She also had reduced respiratory reserves and a restrictive lung disease. Both curves were rigid on supine maximum traction radiographs. She underwent a single-stage anterior and posterior spinal arthrodesis with pedicle hook/sublaminar wire/screw and rod instrumentation and autologous rib graft, supplemented by allograft bone and made a good postoperative recovery. Her scoliosis was corrected to 25[degree sign] and 24[degree sign] and a balanced spine in the coronal and sagittal planes was achieved. At latest follow-up beyond skeletal maturity (3 years post-surgery) she had an excellent cosmetic outcome with no loss of deformity correction, no detected pseudarthrosis and a normal level of activities. Scoliosis can occur in patients with Treacher Collins syndrome with the deformity demonstrating significant deterioration around the adolescent growth spurt. A high index of awareness will allow for an early diagnosis and scoliosis correction at a stage when this can be safer and performed through a single-stage posterior procedure. If the deformity is detected at a later age and stage of growth as occurred in our patient, more complex surgery is required and this increases the risk for major morbidity and potential mortality. Surgical treatment can correct the deformity, balance the spine and restore cosmesis, as well as prevent mechanical back pain and respiratory complications if the scoliosis progressed to cause severe thoracic distortion. A thorough preoperative assessment can diagnose associated comorbidities and reduce the risk for postoperative complications.

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