BRF1 mutations alter RNA polymerase III-dependent transcription and cause neurodevelopmental anomalies.

Abstract

RNA polymerase III (Pol III) synthesizes tRNAs and other small noncoding RNAs to regulate protein synthesis. Dysregulation of Pol III transcription has been linked to cancer, and germline mutations in genes encoding Pol III subunits or tRNA processing factors cause neurogenetic disorders in humans, such as hypomyelinating leukodystrophies and pontocerebellar hypoplasia. Here we describe an autosomal recessive disorder characterized by cerebellar hypoplasia and intellectual disability, as well as facial dysmorphic features, short stature, microcephaly, and dental anomalies. Whole-exome sequencing revealed biallelic missense alterations of BRF1 in three families. In support of the pathogenic potential of the discovered alleles, suppression or CRISPR-mediated deletion of brf1 in zebrafish embryos recapitulated key neurodevelopmental phenotypes; in vivo complementation showed all four candidate mutations to be pathogenic in an apparent isoform-specific context. BRF1 associates with BDP1 and TBP to form the transcription factor IIIB (TFIIIB), which recruits Pol III to target genes. We show that disease-causing mutations reduce Brf1 occupancy at tRNA target genes in Saccharomyces cerevisiae and impair cell growth. Moreover, BRF1 mutations reduce Pol III-related transcription activity in vitro. Taken together, our data show that BRF1 mutations that reduce protein activity cause neurodevelopmental anomalies, suggesting that BRF1-mediated Pol III transcription is required for normal cerebellar and cognitive development.

• Authors: Guntram Borck, Friederike Hög, Maria Lisa Dentici, Perciliz L Tan, Nadine Sowada, Ana Medeira, Lucie Gueneau, Holger Thiele, Maria Kousi, Francesca Lepri, Larissa Wenzeck, Ian Blumenthal, Antonio Radicioni, Tito Livio Schwarzenberg, Barbara Mandriani, Rita Fischetto, Deborah J Morris-Rosendahl, Janine Altmüller, Alexandre Reymond, Peter Nürnberg, Giuseppe Merla, Bruno Dallapiccola, Nicholas Katsanis, Patrick Cramer, Christian Kubisch
• Journal: Genome research (Genome Res) Vol. 25 Issue 2 Pg. 155-66 (Feb 2015) ISSN: 1549-5469 [Electronic] United States
• PMID: 25561519 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 Borck et al.; Published by Cold Spring Harbor Laboratory Press.

Chemical References

• BRF1 protein, human
• Protein Isoforms
• TATA-Binding Protein Associated Factors
• RNA Polymerase III

Topics

• Abnormalities, Multiple (diagnosis, genetics)
• Adolescent
• Amino Acid Sequence
• Amino Acid Substitution
• Animals
• Brain (pathology)
• Cell Proliferation
• Child
• Child, Preschool
• Exome
• Facies
• Female
• High-Throughput Nucleotide Sequencing
• Humans
• Infant
• Intellectual Disability (diagnosis, genetics)
• Magnetic Resonance Imaging
• Male
• Models, Molecular
• Molecular Sequence Data
• Mutation
• Pedigree
• Phenotype
• Protein Conformation
• Protein Isoforms
• RNA Polymerase III (metabolism)
• Siblings
• Syndrome
• TATA-Binding Protein Associated Factors (chemistry, genetics, metabolism)
• Transcription, Genetic
• Zebrafish