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Title: Genomic anatomy of the Tyrp1 (brown) deletion complex

Abstract

Chromosome deletions in the mouse have proven invaluable in the dissection of gene function. The brown deletion complex comprises >28 independent genome rearrangements, which have been used to identify several functional loci on chromosome 4 required for normal embryonic and postnatal development. We have constructed a 172-bacterial artificial chromosome contig that spans this 22- egabase (Mb) interval and have produced a contiguous, finished, and manually annotated sequence from these clones. The deletion complex is strikingly gene- oor, containing only 52 protein-coding genes (of which only 39 are supported by human homologues) and has several further notable genomic features, including several segments of >1 Mb, apparently devoid of a coding sequence. We have used sequence polymorphisms to finely map the deletion breakpoints and identify strong candidate genes for the known phenotypes that map to this region, including three lethal loci (l4Rn1, l4Rn2, and l4Rn3) and the fitness mutant brown-associated fitness (baf). We have also characterized misexpression of the basonuclin homologue, Bnc2, associated with the inversion-ediated coat color mutant white-based brown (Bw). This study provides a molecular insight into the basis of several characterized mouse mutants, which will allow further dissection of this region by targeted or chemical mutagenesis.

Authors:
 [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mouse Genetics Research Facility
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
936555
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proceedings of the National Academy of Sciences; Journal Volume: 103; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ANATOMY; CHROMOSOMES; COLOR; CONTIGS; FUNCTIONALS; GENES; MUTAGENESIS; MUTANTS; brown locus; chromosome deletion; mouse genome sequence

Citation Formats

Hunsicker, Patricia R, and Johnson, Dabney K. Genomic anatomy of the Tyrp1 (brown) deletion complex. United States: N. p., 2006. Web.
Hunsicker, Patricia R, & Johnson, Dabney K. Genomic anatomy of the Tyrp1 (brown) deletion complex. United States.
Hunsicker, Patricia R, and Johnson, Dabney K. Sun . "Genomic anatomy of the Tyrp1 (brown) deletion complex". United States. doi:.
@article{osti_936555,
title = {Genomic anatomy of the Tyrp1 (brown) deletion complex},
author = {Hunsicker, Patricia R and Johnson, Dabney K},
abstractNote = {Chromosome deletions in the mouse have proven invaluable in the dissection of gene function. The brown deletion complex comprises >28 independent genome rearrangements, which have been used to identify several functional loci on chromosome 4 required for normal embryonic and postnatal development. We have constructed a 172-bacterial artificial chromosome contig that spans this 22- egabase (Mb) interval and have produced a contiguous, finished, and manually annotated sequence from these clones. The deletion complex is strikingly gene- oor, containing only 52 protein-coding genes (of which only 39 are supported by human homologues) and has several further notable genomic features, including several segments of >1 Mb, apparently devoid of a coding sequence. We have used sequence polymorphisms to finely map the deletion breakpoints and identify strong candidate genes for the known phenotypes that map to this region, including three lethal loci (l4Rn1, l4Rn2, and l4Rn3) and the fitness mutant brown-associated fitness (baf). We have also characterized misexpression of the basonuclin homologue, Bnc2, associated with the inversion-ediated coat color mutant white-based brown (Bw). This study provides a molecular insight into the basis of several characterized mouse mutants, which will allow further dissection of this region by targeted or chemical mutagenesis.},
doi = {},
journal = {Proceedings of the National Academy of Sciences},
number = 10,
volume = 103,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • No abstract prepared.
  • The mouse Tyrp1 deletion complex is a valuable resource for high-resolution mapping of genes and phenotypes to the central region of Chromosome (Chr) 4. The distal part of the complex is homologous to human Chr 9p21-23, and the authors have used the available radiation hybrid maps to identify human transcripts in the region. They localize seven genes to a human YAC contig that spans the full extent of the distal deletion complex and show that the mouse homologs of four of these, including Cer1, map within the complex. On the basis of location and/or expression, they exclude genes as candidatesmore » for several known phenotypes in the region and identify a candidate transcript for the neonatal lethal phenotype 1(r)Rn2.« less
  • Mutations in distant regulatory elements can negatively impact human development and health, yet due to the difficulty of detecting these critical sequences we predominantly focus on coding sequences for diagnostic purposes. We have undertaken a comparative sequence-based approach to characterize a large noncoding region deleted in patients affected by Van Buchem disease (VB), a severe sclerosing bone dysplasia. Using BAC recombination and transgenesis we characterized the expression of human sclerostin (sost) from normal (hSOSTwt) or Van Buchem(hSOSTvb D) alleles. Only the hSOSTwt allele faithfully expressed high levels of human sost in the adult bone and impacted bone metabolism, consistent withmore » the model that the VB noncoding deletion removes a sost specific regulatory element. By exploiting cross-species sequence comparisons with in vitro and in vivo enhancer assays we were able to identify a candidate enhancer element that drives human sost expression in osteoblast-like cell lines in vitro and in the skeletal anlage of the E14.5 mouse embryo, and discovered a novel function for sclerostin during limb development. Our approach represents a framework for characterizing distant regulatory elements associated with abnormal human phenotypes.« less
  • Chromosomal rearrangements with duplication of the lamin B1 (LMNB1) gene underlie autosomal dominant adult-onset demyelinating leukodystrophy (ADLD), a rare neurological disorder in which overexpression of LMNB1 causes progressive central nervous system demyelination. However, we previously reported an ADLD family (ADLD-1-TO) without evidence of duplication or other mutation in LMNB1 despite linkage to the LMNB1 locus and lamin B1 overexpression. By custom array-CGH, we further investigated this family and report here that patients carry a large (~660 kb) heterozygous deletion that begins 66 kb upstream of the LMNB1 promoter. Lamin B1 overexpression was confirmed in further ADLD-1-TO tissues and in amore » postmortem brain sample, where lamin B1 was increased in the frontal lobe. Through parallel studies, we investigated both loss of genetic material and chromosomal rearrangement as possible causes of LMNB1 overexpression, and found that ADLD-1-TO plausibly results from an enhancer adoption mechanism. The deletion eliminates a genome topological domain boundary, allowing normally forbidden interactions between at least three forebrain-directed enhancers and the LMNB1 promoter, in line with the observed mainly cerebral localization of lamin B1 overexpression and myelin degeneration. Finally, this second route to LMNB1 overexpression and ADLD is a new example of the relevance of regulatory landscape modifications in determining Mendelian phenotypes.« less