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Linkage mapping of the retinol-binding protein 4 (RBP4) gene to porcine Chromosome 14

L.A. Messer, a L. Wang, 1 J. Yelich, 2 D. Pomp, 2 R.D. Geisert, 2 M.F. Rothschild 1

~Department of Animal Science, Iowa State University, Ames, Iowa 50011-3150, USA 2Department of Animal Science, Oklahoma State University, Stillwater, Oklahoma 74078, USA

Received: 3 October 1995 / Accepted: 15 January 1996

Species: Pig Locus name: Retinol-binding protein 4 Locus symbol: RBP4 Map positions: Loci order of a portion of the distal end of Chro- mosome (Chr) 14: -ACTN2-1.7-ACTA1-2.7-PLAU-O-SW210- 8.2-S0169-9.9-S00 72-11.1 -SO00 7-7.3 -RBP4- l 6.2-S0116- 20.0-Sw761-36.1-S0015. Method o f mapping: Six three-generation PiGMaP families of Meishan x Large White and European Wild Boar x Large White pigs [1]. Molecular reagents: The porcine RBP4 gene probe was obtained by RT-PCR amplification of a 311-bp fragment from day 12 por- cine blastocysts with primers designed based on pig cDNA se- quences. The 5' primer (5'-TTCCGAGTCAAAGAGAACTTCG- 3') represents nucleotides 79-100, and the 3' primer (5'- TCATAGTCCGTGTCGATGATCC-3 ' ) represents nucleotides 368-389 [3]. Amplified product was purified and radiolabeled with 32p by random priming. Allele detection: A SacI polymorphism was detected in pig geno- mic DNA by hybridization of Southern blots with the pig RBP4 probe at a final wash stringency of 0,7 x SSC and 0.2% SDS at 65~ Autosomal Mendelian inheritance was observed in two

Correspondence to: M.F. Rothschild

Mammalian Genome 7, Brief Data Reports

Table 1. Results of the two-point linkage analysis for RBP4.

Recombination Marker 1 Marker 2 fraction Lod score

RBP4 S0007 0.07 17.02 RBP4 S0116 0.21 4.63 RBP4 SW210 0.27 3.50

polymorphic fragments detected at 12.1 kb and 7.8 kb. Sixty-two unrelated pigs from eight breeds were genotyped for RBP4. Fre- quencies of the 12.1-kb fragment were 0.55 in Landrace (n = 10), 0.75 in Duroc (n = 10), 1.0 in Yorkshire (n = 5), 0.50 in Chester White (n = 4), 0.59 in Large White (n = 11), 1.0 in Hampshire (n = 5), 0.80 in Meishan (n = 15), and 1.0 in Wild Boar (n = 2). Previously identified homologs: Human RBP4 maps to 10q23-24 [4] and mouse Rbp-4 is localized to the distal end of Chr 19 [5]. Discussion: Retinol-binding protein is a major secretory product of the pig conceptus prior to implantation [3]. Increased production of RBP4 during the rapid morphological developmental period of pig blastocyst elongation [8], which is a critical period for embry- onic survival, suggests that RBP4 may be an interesting candidate gene for investigation of QTL for reproduction in pigs.

Linkage analysis was performed with the CRIMAP version 2.4 software package [2]. The two-point linkage analysis produced significant lod scores (>3.0) of RBP4 with loci S0007, S0116, and SW210 on porcine Chr 14 (Table 1). The order of the loci on our map is in agreement with the new loci arrangement of the PiGMaP map [1] of Chr 14 according to Kapke and associates [6], with the exception of the rearrangement of loci S0007 and S0072. The addition of RBP4 to the revised PiGMaP map further increases the sex-averaged map length from 193 cM to 202 cM. Placement of RBP4 on Chr 14 strengthens the homology between porcine Chr 14 and human Chr 10 [7].

Acknowledgments: The authors thank R.G. Larson and S. Kenealy for their technical assistance. This work was supported in part by the Iowa Agri- culture and Home Economics Experiment Station, Ames, Journal paper No. J-16549, Project No. 3043. Approval for publication was also received from the Oklahoma Agricultural Experiment Station. This work is part of the PiGMaP international genetic mapping collaboration and supported by the E.C. Bridges program. Reference family DNA was provided by PiGMaP collaborators in Scotland, France, Netherlands and Sweden.

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