|
|
|
|
Published online before print
February 3, 2006, 10.1101/gr.4563306 Genome Res. 16:436-440, 2006 ©2006 by Cold Spring Harbor Laboratory Press; ISSN 1088-9051/06 $5.00
Resources Utilization of a whole genome SNP panel for efficient genetic mapping in the mouse1 Genetics Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA 2 Hematology Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA 3 Harvard Partners Center for Genetics and Genomics, Harvard Medical School, Cambridge, Massachusetts 02139, USA 4 Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA 5 Departments of Biostatistics and Computational Biology, Dana Farber Cancer Institute and Harvard School of Public Health, Boston, Massachusetts 02115, USA 6 Center for Functional Genomics, Northwestern University, Evanston, Illinois 60208, USA 7 Howard Hughes Medical Institute, Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA 8 Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, USA
Phenotype-driven genetics can be used to create mouse models of human disease and birth defects. However, the utility of these mutant models is limited without identification of the causal gene. To facilitate genetic mapping, we developed a fixed single nucleotide polymorphism (SNP) panel of 394 SNPs as an alternative to analyses using simple sequence length polymorphism (SSLP) marker mapping. With the SNP panel, chromosomal locations for 22 monogenic mutants were identified. The average number of affected progeny genotyped for mapped monogenic mutations is nine. Map locations for several mutants have been obtained with as few as four affected progeny. The average size of genetic intervals obtained for these mutants is 43 Mb, with a range of 1783 Mb. Thus, our SNP panel allows for identification of moderate resolution map position with small numbers of mice in a high-throughput manner. Importantly, the panel is suitable for mapping crosses from many inbred and wild-derived inbred strain combinations. The chromosomal localizations obtained with the SNP panel allow one to quickly distinguish between potentially novel loci or remutations in known genes, and facilitates fine mapping and positional cloning. By using this approach, we identified DNA sequence changes in two ethylnitrosourea-induced mutants.
Until recently, genetic mapping in the mouse was performed most efficiently by analysis of simple sequence length polymorphism (SSLP) markers both for initial identification of chromosomal (Chr.) localization and for high-resolution mapping (Dietrich et al. 1994
Advances in genome sequencing have led to the discovery of thousands of single nucleotide polymorphisms (SNPs) in the mouse genome (Lindblad-Toh et al. 2000 We sought to utilize SNP genotyping as an alternative to microsatellite marker analysis for mapping mutations in the mouse. We generated a whole-genome panel of 394 SNPs that can be used to map monogenic mutations in a high-throughput manner with small numbers of mice and without prior consideration of genetic background. By genotyping 28 inbred and wild-derived strains and by using the panel to identify map locations for 22 mutations, we demonstrate that the SNP panel is effective at identifying chromosomal localizations at moderate resolution by analyzing small numbers of affected progeny. Two ethylnitrosourea (ENU)-induced mutants that were mapped to subchromosomal regions using the SNP panel were further fine-mapped, and single base-pair mutations were identified by sequencing of candidate genes.
SNP panel description SNPs were selected from a larger pool of published SNPs (Wiltshire et al. 2003 The utility of the panel for mapping a mutation with a particular genetic cross depends not only on the number of informative SNPs but also on the distribution of those informative SNPs throughout the genome. With the exception of closely related strains, there is adequate genome coverage of informative SNPs for most strain pairs. Because of the bias in SNP selection among a few inbred strains, it is not unexpected that large gaps in informative SNPs will exist for even highly polymorphic strains; e.g., C57BL/6J and FVB/NJ have 211 informative SNPs with two large gaps between SNPs of 67 (Chr. 7) and 63 Mb (Chr. 14).
SNP-based mapping of monogenic mutations
hydrops fetalis (hyft) is a recessive ENU-induced perinatal lethal mutant with dramatic embryonic growth deficiency, intravascular fluid accumulation, and frequent intrauterine demise (Herron et al. 2002
Utilizing SNP genotyping analyses to facilitate positional cloning Even low-resolution chromosomal localization allows one to quickly distinguish between potentially novel loci or remutations in known genes. This is of particular utility as a means to prioritize analyses in cases where large numbers of mutants are generated, such as ENU mutagenesis screens. The SNP-based genetic mapping of both baldy and hyft suggested that both were remutations in known genes. Allelism between baldy and the hairless (hr) mutation was investigated based on the similar skin and hair phenotypes and map positions on distal 14 (Cachon-Gonzalez et al. 1994
Sequencing of the hr gene in baldy homozygotes revealed a single base pair change from C to T in exon 2, a noncoding exon, introducing an out-of-frame ATG upstream of the normal translation initiation site (Fig. 3). hr transcript is present in baldy affecteds; however, hr protein expression in skin is dramatically reduced (data not shown). Of four alleles of hr in which the sequence change is known, this is the first known mutation in a 5' noncoding region (Blake et al. 2003
High-resolution mapping of 11 hyft affected progeny with SSLP markers narrowed the genetic interval to 10 Mb, between D7Mit89 (51.0Mb) and D7Mit182 (61.6 Mb) (data not shown). The insulin-like growth factor 1 receptor (Igf1r; 54.9 Mb) was tested as a candidate for the mutated locus because of the similarity between the embryonic growth defect in hyft and Igf1r loss-of-function mice (Liu et al. 1993 We have shown that by selecting several hundred SNPs based on polymorphism in a few inbred strains, the density and informativeness of our SNP panel is sufficient to map mutations with many strain pairs, including inbred and wild-derived strain pairs. The 22 monogenic mutants were mapped utilizing crosses with a combined total of 11 different strain combinations (Table 1). Even for complex genetic studies, this SNP panel may provide a good starting point for whole-genome linkage analyses and for the design of additional panels for higher-resolution mapping. For example, preliminary results of a genetic modifier study suggests that this 394 SNP set identified a modifying locus of the DDK syndrome embryonic lethal phenotype in two wild-derived M. musculus domesticus inbred strains (LOD score = 10.1; 77 N2 mice) (F. Ideraabdullah and F. Pardo-Manuel de Villena, pers. comm.). Given the continuing advances in technology for high-throughput SNP genotyping, we anticipate that analyses using standardized genome-wide SNP panels will become a routine component of genetic studies in the mouse.
SNP assay design and genotyping Polymerase chain reaction (PCR) primers and mini-sequencing extension primers were designed for each SNP, and SNPs were multiplexed into a maximum of five-plex pools by using Spectrodesigner software (Sequenom). Genomic DNA (2.5 ng, 1.25 ng/µL) was PCR-amplified in a 5 µL reaction containing 0.1 U HotStar Taq polymerase and 1x HotStar Taq PCR Buffer (Qiagen), 2.5 mM MgCl2, 200 µM of each dNTP (USB), and 50 nM each PCR primer. Samples were incubated for 15 min at 95°C; followed by 45 cycles of 20 sec at 95°C, 30 sec at 56°C, and 1 min at 72°C; followed by 3 min at 72°C on a GeneAmp PCR System 9700 (Applied Biosystems). Excess dNTPs were removed from the reaction by addition of 0.3 U shrimp alkaline phosphatase (SAP; USB) in Thermosequenase RCTN Buffer (Amersham Biosciences) for 20 min at 37° C followed by 5 min at 85°C. Amplified PCR products were used as a template in a second, modified, single-primer mini-sequencing reaction. Extension reactions contain 600 nM of extension primer, 50 uM dNTP, and ddNTP in Thermosequenase RCTN buffer, and 0.126 U Thermosequenase. Samples were heated at 94°C for 2 min followed by 45 cycles of 5 sec at 94°C, 5 sec at 52°C, and 5 sec at 72°C. The mini-sequencing reaction is then desalted by addition of SpectroClean resin (Sequenom) and spotted onto SpectroCHIPS (Sequenom) by using a nanoliter-plotting robot (SpectroPLOTTER, Sequenom). Chips were individually analyzed by using the Brukker Bi-flex MALDI-TOF mass spectrometer (Sequenom). The resulting spectra are converted to genotype data by using SpectroTYPER-RT software (Sequenom).
Genomic DNA preparation for SNP genotyping Genomic DNA from all inbred and wild-derived strains, with the exception of 129S6SvEv (Taconic), was obtained from The Jackson Laboratory DNA Resource (Bar Harbor, ME) or from mice that were purchased from The Jackson Laboratory (JAX) and maintained on-site. 129S4SvJae DNA was obtained from the DNA stock 002497 (JAX). Genomic DNA was prepared from mouse tails either by a standard proteinase K phenol-chloroform extraction method or by using the PUREGENE Purification Kit for cells and tissue (Gentra Systems).
Polymorphism matrix
Mice Strains C57BL/6J (B6) and FVB/NJ (FVB) used for genetic mapping of hyft and bldy were obtained from JAX. Complementation testing of baldy was performed with Hrrh-J (RHJ/LeJ, stock 001591; JAX).
Genetic mapping
Mouse Genome Database (Blake et al. 2003
SNP genotyping data analysis
A positive LOD score provides evidence that a SNP marker is close to the mutant locus. We chose the LOD score of three as the threshold, which means the locus is 1000 times more likely to be mutant related than not. dChip software (Lin et al. 2004
Protein extraction and immunoblotting
We thank the following individuals for their contributions: Christopher Walsh, Sally Camper, Jill Karolyi, Bill Pavan, Simon Conway, Miriam Meisler, Catherine Holland, John Schimenti, Larry Jameson, Jeffrey Weiss, Adriana Donovan, Mark Fleming, and Nancy Andrews contributed monogenic mutants for genetic mapping; Yujuan Yun, Lan Wang, Allyson Chesebro, Maura Regan, and Gwen Yarbrough contributed technical assistance; and John Hayden contributed informatics assistance. This work was supported by a grant (U01HD43430) from the National Institutes of Health.
[Supplemental material is available online at www.genome.org.] Article published online ahead of print. Article and publication date are at http://www.genome.org/cgi/doi/10.1101/gr.4563306.
9 Corresponding author.
Blake, J.A., Richardson, J.E., Bult, C.J., Kadin, J.A., Eppig, J.T., and Mouse Genome Database Group. 2003. MGD: The Mouse Genome Database. Nucleic Acids Res. 31: 193195. Cachon-Gonzalez, M.B., Fenner, S., Coffin, J.M., Moran, C., Best, S., and Stoye, J.P. 1994. Structure and expression of the hairless gene of mice. Proc. Natl. Acad. Sci. 91: 77177721. Dietrich, W.F., Miller, J.C., Steen, R.G., Merchant, M., Damron, D., Nahf, R., Gross, A., Joyce, D.C., Wessell, M., Dredge, R.D., et al. 1994. A genetic map of the mouse with 4006 simple sequence length polymorphisms. Nat. Genet. 7: 220245.[CrossRef][Medline] Durbin, R., Eddy, S., Krogh, A., and Mitchison, G. 1999. Biological sequence analysis: Probabilistic models of proteins and nucleic acids. Cambridge University Press, Cambridge, UK. Fraser, K.A., Wade, C.M., Hinds, D.A., Patil, N., Cox, D.R., and Daly, M.J. 2004. Segmental phylogenetic relationships of inbred mouse strains revealed by fine-scale analysis of sequence variation across 4.6 Mb of mouse genome. Genome Res. 14: 14931500. Grupe, A., Germer, S., Usuka, J., Aud, D., Belknap, J.K., Klein, R.F., Ahluwalia, M.K., Higuchi, R., and Peltz, G. 2001. In silico mapping of complex disease-related traits in mice. Science 292: 19151918. Herron, B.J., Lu, W., Rao, C., Liu, S., Peters, H., Bronson, R.T., Justice, M.J., McDonald, J.D., and Beier, D.R. 2002. Efficient generation and mapping of recessive developmental mutations using ENU mutagenesis. Nat. Genet. 30: 185189.[CrossRef][Medline] Liao, G., Wang, J., Guo, J., Allard, J., Cheng, J., Ng, A., Shafer, S., Puech, A., McPherson, J.D., Foemzler, D., et al. 2004. In silico genetics: Identification of a functional element regulating H2-E Lin, M., Wei, L.J., Sellers, W.R., Lieberfarb, M., Wong, W.H., and Li, C. 2004. dChipSNP: Significance curve and clustering of SNP-arraybased loss-of-heterozygosity data. Bioinformatics 20: 12331240. Lindblad-Toh, K., Winchester, E., Daly, M.J., Wang, D.G., Hirschhorn, J.N., Laviolette, J.P., Ardlie, K., Reich, D.E., Robinson, E., Sklar, P., et al. 2000. Large-scale discovery and genotyping of single-nucleotide polymorphisms in the mouse. Nat. Genet. 24: 381386.[CrossRef][Medline] Liu, J.P., Baker, J., Perkins, A.S., Robertson, E.J., and Efstratiadis, A. 1993. Role of insulin-like growth factors in embryonic and postnatal growth. Cell 75: 7382.[CrossRef][Medline] Neuhaus, I.M. and Beier, D.R. 1998. Efficient localization of mutations by interval haplotype analysis. Mamm. Genome 9: 150154.[CrossRef][Medline] Owens, S.E., Broman, K.W., Wiltshire, T., Belmore, J.B., Bradley, K.M., Smith, J.R., and Southard-Smith, E.M. 2005. Genome-wide linkage identifies novel modifier loci of aganglionosis in the Sox10Dom model of Hirschsprung disease. Hum. Mol. Genet. 14: 15491558. Petkov, P.M., Ding, Y., Cassell, M.A., Zhang, W., Wagner, G., Sargent, E.E., Asquith, S., Crew, V., Johnson, K.A., Robinson, P., et al. 2004. An efficient SNP system for mouse genome scanning and elucidating strain relationships. Genome Res. 14: 18061811. Pletcher, M.T., McClurg, P., Batalov, S., Su, A.I., Barnes, S.W., Lagler, E., Korstanje, R., Wang, X., Nusskern, D., Bogue, M.A., et al. 2004. Use of a dense single nucleotide polymorphism map for in silico mapping in the mouse. PLoS Biol. 2: e393.[CrossRef][Medline] Wade, C.M., Kulbokas III, E.J., Kirby, A.W., Zody, M.C., Mullikin, J.C., Lander, E.S., Lindblad-Toh, K., and Daly, M.J. 2002. The mosaic structure of variation in the laboratory mouse genome. Nature 420: 574578.[CrossRef][Medline] Wiltshire, T., Pletcher, M.T., Batalov, S., Barnes, S.W., Tarantino, L.M., Cooke, M.P., Wu, H., Smylie, K., Santrosyan, A., Copeland, N.G., et al. 2003. Genome-wide single-nucleotide polymorphism analysis defines haplotype patterns in mouse. Proc. Natl. Acad. Sci. 100: 33803385.
Received August 12, 2005; accepted in revised format December 6, 2005. This article has been cited by other articles:
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||