Annual Report of Multistate Research Activity

PROJECT NUMBER: NRSP-8
PROJECT TITLE: NRSP-8: Swine Species Genome Committee
PERIOD COVERED: January 1 to December 31, 2004
DATE OF THIS REPORT: February 10, 2005
ANNUAL MEETING DATE(S): January 15, 2005

PARTICIPANTS: A list of those who attended the meeting is posted at http://www.genome.iastate.edu/ community/NRSP8/2004/index.html.

BRIEF SUMMARY OF MINUTES OF ANNUAL MEETING: The URL for the meeting minutes is http://www. genome.iastate.edu/community/NRSP8/2004/index.html.

ACCOMPLISHMENTS AND IMPACTS: In this section focus on intended outcomes and potential impacts. This information should be built around the activity's milestones. Also, describe plans for the coming year in no more than one or two short paragraphs. For clarity, it may be helpful to present the accomplishments separately for each objective.

Progress Toward Objective 1: Enhance and integrate genetic and physical maps of agriculturally important animals for cross species comparisons and sequence annotation.

BARC and Baylor Univ researchers, with the ISAG SLA committee, established an internationally recognized nomenclature to identify and classify SLA class I gene polymorphisms. This will serve as a basis for determining critical genetic effects on infectious disease and vaccine responses. They have made data fully accessible at an international website, the IPD-MHC Sequence Database website: www.ebi.ac.uk/ipd/mhc/sla/nomenclature.html.

A large number of genes continue to be identified and mapped by ISU researchers. An emphasis has been made (and will continue to be made) on genes that improve the comparative map as well as in connecting the genetic and physical pig genome maps. Several new genes that may be important QTL are being mapped by ISU researchers. These include genes associated with cured meat quality and sow longevity. QTL for several meat quality traits have been discovered. Additional fine mapping is underway and positional candidate genes are being considered. Mapping of over 400 comparative loci to pig chromosomes SSC1, 4, 7, 8 and X adds additional information to comparative maps.

ISU mapping results revealed possible homologies for SSC1, 3, 5, 6, 12 and 14 with the human genome and refine synteny breakpoints for one chromosome, SSC7. This information allows comparative information from human to be used for genome analysis in the pig. Comparative mapping between human and pig chromosomes corroborates chromosome painting results in that approximately 85-90% of loci map to expected locations, but also demonstrate that pig gene order cannot be predicted from the order of human genes within conserved syntenic groups.

Research on developing new SNPs segregating within purebred commercial lines of pigs is in progress at NCSU and at MARC.

UNE researchers completed the physical mapping (SCHP, RHP) of reproduction-relevant expressed genes (~750 EST). They are completing SNP discovery for 50 differentially expressed genes in the ovarian follicle, with a goal of 3-5 SNPs per locus, and plan to use those SNPs for large-scale (n=1600 pigs) association studies in commercially relevant maternal lines of pigs.

The Pig Reproduction EST Consortium project has significantly increased the density of Type I markers on the pig physical map, focusing on genes relevant to economically important traits. This project has enhanced the comparative maps between pig and human/mouse, which will be facilitative for porcine gene discovery. Sequencing and mapping of ESTs, together with resource development such as normalized libraries and microarrays, will be useful for positional cloning efforts and characterizing important biological/physiological events controlling economically relevant traits.

UNV researchers used Carthagene (http://www.inra.fr/bia/T/schiex/Export/WABI.pdf) to calculate an updated version of the 2nd Generation pig human comparative map (IMpRH 7000Rad panel). Carthagene is also the software of choice in developing the IMNpRH12,000-rad map. Markers that introduced new homologies to the comparative map are reevaluated based on their multipoint linkage assignment (using the IMpRH mapping tool), rather than on their 2pt LOD value. These maps will be transferred to the FTP site as they become available. They have assigned a total of 2774 ESTs to all chromosomes on the IMNpRH12,000-rad panel. A total of 1918 (94% 2035 ESTs) ESTs on the IMpRH7000rad map have been assigned to the IMNpRH12,000-rad map. The location of these ESTs is currently being finalized and will be available on their web sites (www.toulouse.inra.fr/lgc/lgc/, http://www.ag.unr.edu/ab/standard.htm), shortly.

A comprehensive RH map of SSC3 was constructed at WSU with a total of 116 genes/markers, including 16 that have been placed on the cytogenetic map and 21 on the linkage map. The retention frequency of these 116 genes/markers varied from 8.5 to 53.3% with an average of 27.62%. Overall, SSC3 had a total of 11 conserved segments paired with human, 13 with dog, 17 with rat and 22 with mouse, respectively. Alignment of ~192 Mb of orthologous regions in these five species led to the identification of provisional conserved ancestral blocks (CABs) and the characterization of breakpoint regions, which provides an alternative for further determination of the evolutionary makeup of mammalian genomes.

Progress Toward Objective 2: Facilitate integration of genomic, transcriptional, proteomic and metabolomic approaches toward better understanding of biological mechanisms underlying economically important traits.

BARC researchers have provided means to study expression and function of additional immune genes in normal breeding populations to identify early responders which might be more disease resistant/susceptible. New work in porcine reproductive and respiratory syndrome virus (PRRSV) resistance with UNE researchers may help identify pigs which are more disease resistant and the protective mechanisms they employ to induce resistance.

ISU researchers have used two molecular techniques to identify some of the genes which increase or decrease expression levels in the early response to Salmonella choleraesuis or S. typhimurium infection. These are subtractive suppression hybridization (SSH) and microarray. Genes include signal transduction and steroid biosynthesis which are involved in the embryo elongation process. ISU and NADC researchers have begun to analyze the lungs of pigs infected with S. choleraesuis by using the NRSP8 funded long oligonucleotide microarray, and find 57 genes with some statistical evidence (P <0.001) for differential expression; of the 40 genes from this group with human functional annotation, 40% are related to the immune system. The transcriptional profiling results were verified by quantitative techniques with BARC researchers.

Transcriptional profiling of skeletal muscle tissue at Michigan State Univ. reveals important genes in the pathways regulating skeletal muscle growth and development. Their development of a unique pig resource population provides a novel resource for identifying QTL associated with growth and carcass merit in pigs.

NCSU researchers are characterizing changes in allelic frequencies for two RFLPs associated with the follistatin gene in a line of pigs selected for increased litter size (LS). In a separate project they are working to identify genes associated with adipose metabolism. For this they are analyzing gene expression during t10c12-CLA-induced body fat reduction in a polygenic obese line of mice.

In an effort to identify genes responsible for anti-microbial responses in the gut, UMN researchers isolated expressed sequence tags (EST) from an activated porcine Peyer’s patch cDNA library. 3687 ESTs, representing 2414 unique nucleotide sequences were analyzed and spotted onto a microarray for gene expression profiling. Approximately 30% of these ESTs BLAST to genes of unknown function and 20% appear to be novel, i.e., have no known homology in the public databases. To determine chromosomal location, PCR-based mapping was performed across a swine radiation hybrid panel; 125 ESTs were mapped with a lod score > 6.0. These ESTs therefore should provide insight into early immune mechanisms and processes activated in Peyer’s patches.

Islet gene expression profiles were assessed at UMN using the NRSP8 funded porcine 70-mer oligonucleotide microarray and real-time PCR. Microarray data were analyzed by direct pairwise comparison between culture conditions and by loop design using GeneSpring and R/maanova, respectively. Cytokine treatment resulted in increased expression of genes involved in stress, immune response, apoptosis, and cellular defense. Islets cultured under conditions of elevated glucose showed increased expression of genes involved in intracellular protein transport, glucose and lipid metabolism, and stress response. Transcriptional profiling of the response of porcine islet beta cells to inflammatory and hyperglycemic conditions will help identify molecular targets that are likely to protect porcine islets during islet isolation and engraftment.

Integration of genomics/proteomics/metabolomics approaches may be a mechanism to successfully bridge the gap between predisposition and physiology and enable more accurate selection of candidate genes underlying a QTL peak. By identifying SNPs within differentially expressed genes, UNE researchers are testing the hypothesis that a subset of genes regulating reproduction at the physiological level will harbor genetic variation controlling genetic predisposition to reproductive phenotypes.

Energy metabolism is a complex process determined by the action of several endogenous and exogenous factors. Difference between energy intake and energy dissipation is reflected in changes of body composition. In eukaryotes the mitochondrial function and copy-number can be increased in response to external stimuli. At WSU mitochondrial transcription factor A (TFAM) full length cDNA was cloned and sequenced. A SNP was developed and genotyped on ~250 animals from 12 pig breeds, including 7 Chinese and 5 European/American pig breeds.

Progress Toward Objective 3: Facilitate and implement bioinformatic tools to extract, analyze, store and disseminate information.

Database development is continuing at ISU. An EST database has been developed and is quite useful. ISU researchers developed a relational pig quantitative trait loci (QTL) database (PigQTLDB) to integrate all available pig QTL data in the public domain and thus facilitate the use of QTL data in further studies. PigQTLdb has been well used since its release last December (http://www.animalgenome.org/QTLdb/). They developed a trait ontology to standardize names of traits and to simplify organization of the data making it possible to compare primary data from diverse sources and methods. The database contains all pig QTL data published during the past 10+ years. The database and its peripheral tools were made to compare, confirm, and locate on pig chromosomes the most feasible location for a candidate gene responsible for quantitative trait(s) important to pig production. To date, 791 QTL from 73 publications have been curated into the database. Those QTLs cover more than 300 different traits. Contact Zhiliang Hu (zhu@iastate.edu) with any suggested improvements or additional data to add to the database. These data have been submitted to the Gene and Map Viewer resources at NCBI, where the information about markers has been matched to marker records in NCBI's UniSTS database. This allows automatic matching of markers to public sequence data by e-PCRand data retrieval from NCBI resources.

Efforts at ISU and UMN have been aimed at developing better annotation of the NRSP8 funded porcine 70-mer oligonucleotides for microarray data analyses.

WSU researchers have take 3 steps to collect and generate full-length cDNA sequences of orthologous genes in livestock species, i.e., puzzle sorting, puzzle retrieving and puzzle making for a final puzzle solving. They have developed a bioinformatics tool, ELF-Walking (electronic flanking walking) to facilitate large-scale in silico cloning of full-length cDNA sequences by mining the sequence databases. Using 21,775 human coding genes as references, they were able to generate unique full-length cDNA sequences of 3,881 genes and partial cDNA sequences of 10,358 genes in pigs, and unique full-length cDNA sequences of 4,308 genes and partial cDNA sequences of 10,785 genes in cattle. All sequence data and annotation information can be downloaded from our Bioinformatics website at http://www.ansci.wsu.edu/programs/bioinformatics/. All of these bioinformatics tools and reagents will contribute to the development of a Livestock Orthologous Gene (LOG) database.

PUBLICATIONS:

List the publications for current year only (with the authors, year, title, journal, etc.).

Bertani G, Gladney C, Johnson RK, Pomp D 2004. Evaluation of gene expression in pigs selected for enhanced reproduction. II: Anterior Pituitary. J Anim Sci 82:32-40.

Blowe, C. D., E. J. Eisen, O. W. Robison, and J. P. Cassady. 2004. Characterization of a line of pigs selected for increased litter size for two RFLPs identified in follistatin. Abstract. J. Anim. Sci Supplement 1.

Caetano AC, JB Edeal, K Burns, RK Johnson, C Tuggle, D Pomp 2005. Physical mapping of the differentially expressed porcine ovarian transcriptome. Animal Genetics (Accepted).

Caetano A, J Ford, RK Johnson, D Pomp 2004. Microarray profiling for differential gene expression in ovaries and ovarian follicles of pigs selected for increased ovulation rate. Genetics 168: 1529-37.

Cao H, Robinson JA, Jiang Z, Melville JS, Golovan SP, Jones MW and Verrinder Gibbins AM. 2004. A high-resolution radiation hybrid map of porcine chromosome 6. Anim. Genet. 35:367-378.

Churchill GA and 101 others including D Pomp 2004. The Collaborative Cross: A community resource for the genetic analysis of complex traits. Nature Genetics 36:1133-1137.

Ciobanu, D.C., J.W.M. Bastiaansen, S.M. Lonergan, H. Thomsen, J.C.M. Dekkers, G.S. Plastow and M.F. Rothschild. 2004. New alleles in calpastatin gene are associated with meat quality traits in pigs. J. Animal Sci. 82:2829-2839.

Ciobanu, D.C., Lonergan, S.M., Bastiaansen, J.W.M., Mileham A, Miculinich, Schultz-Kaster, C., Sosnicki, A.A., Plastow , G.S. and M.F. Rothschild. 2004. Association of new Calpastatin alleles with meat quality traits in commercial pigs. 50th Int. Congress of Meat Science and Technology, Helsinki, Finland.

Dawson HD, Royaee AR, Nishi S, Kuhar D, Schnitzlein WM, Zuckermann F, Urban JF, Lunney JK. 2004. Identification of Key Immune Mediators Regulating T helper 1 Responses in Swine. Vet. Immunol. Immunopathol. 100: 105-111.

Dawson HD, Beshah E, Nishii S, Solano-Aguilar G, Morimoto M, Zhao A, Madden KB, Ledbetter TK, Dubey JP, Shea-Donohue T, Lunney JK, Urban, JF Jr. 2005. Localized multi-gene expression patterns support an evolving Th1/Th2-like paradigm in response to infections with Toxoplasma gondii and Ascaris suum in pigs. Infection and Immunity. 73: 1116-1128.

Dvorak, C.M.T., K.A. Hyland, J.G. Machado, Y. Zhang, S.C. Fahrenkrug, and M.P. Murtaugh. 2004. Gene discovery and expression profiling in porcine Peyer’s patch. Vet. Immunol. Immunopathol. In press.

Ernst, C.W., N.E. Raney, V.D. Rilington, G.A. Rohrer, J.A. Brouillette and P.J. Venta. 2004. Mapping of the FES and FURIN genes to porcine chromosome 7. Anim. Genet. 35:142-143.

Farber, C.R., N.E. Raney, V.D. Rilington, P.J. Venta and C.W. Ernst. 2003. Comparative mapping of genes flanking the human chromosome 12 evolutionary breakpoint in the pig. Cytogenet. Genome Res. 102:139-144.

Flickinger, G.H., C.M.T. Dvorak, J.A. Hendrickson, M.P.Murtaugh, and M.S. Rutherford, 2004. Radiation hybrid mapping of porcine ESTs from porcine Peyer’s Patch. Plant and Animal Genome XII, San Diego, CA, January 11-14.

Gaboreanu, A.M., L. Grapes, A. M. Ramos, J.-J. Kim and M. F. Rothschild. 2004. Characterization of an X-chromosome PCR-RFLP marker associated with fat deposition and growth in the pig. Animal Genetics 35: 401-403.

Galina-Pantoja L, Solano-Aguilar GI, Mellencamp MA, Bastiaansen J, Lunney JK. 2004. Relationship between immune cells and pig growth on a commercial farm. Proc. 18th IPVS Congress, Hamburg, Germany, 2004, Vol. I. p.381.

Gladney C, G Bertani, MK Nielsen, D Pomp 2004. Evaluation of gene expression in pigs selected for enhanced reproduction. I: Ovarian Follicles. J Anim Sci 82:17-31.

Grapes, L., J.C.M. Dekkers, M.F. Rothschild, and R.L. Fernando. 2004. Comparing linkage disequilibrium-based methods for fine mapping quantitative trait loci. Genetics 166: 1561-1570.

Grapes, L., M. Z. Firat, J. C. M. Dekkers, M. F. Rothschild, R. L. Fernando. 2004. Optimal haplotype structure for linkage disequilibrium-based fine mapping of quantitative trait loci. American Association of Animal Science Midwest Region, Mar 15-17, Des Moines, IA

Grapes, L., S. Rudd, R. L. Fernando, M. F. Rothschild. 2004. In silico SNP identification from porcine EST sequences and comparative analysis with human SNP density. Plant and Animal Genome XII, Jan 10-14, San Diego, CA

Grindflek, E, N Hoen, H Sundvold, MF Rothschild, G Plastow and S Lien. 2004. Investigation of a Peroxisome Proliferator Activated Receptor gamma (PPARG) haplotype effect on meat quality and carcass traits in pigs. Anim. Genet 35:238-241.

Holl JW, JP Cassady, D Pomp, RK Johnson 2004. A genome scan for QTL and imprinted regions affecting reproduction in pigs. J Anim Sci 82:3421-3429.

Hu, Z-L, K. Glenn, A. M. Ramos, C. J. Otieno, and M. F. Rothschild. 2004. Expeditor: A Pipeline for Designing Pig Primers Using Human Gene Structure and Pig EST Information. Plant and Animal Genome XII, Jan 10-14, San Diego, CA

Hu, Z-L, Dracheva S , Jang W , Maglott D , Bastiaansen H , Reecy JM , Rothschild MF. 2005. PigQTLDB - A Pig QTL Database. Plant and Animal Genome XIII, Jan 15-19, San Diego, CA (Abstract) P839.

Jiang, Z, Wu X-L, Garcia MD, Griffin KB, Michal JJ, Ott TL, Charley T. Gaskins CT, Raymond W. Wright Jr. 2004. Comparative Gene-based In Silico Transcriptome Analysis of Different Tissues/Organs in Cattle. Genome 47:1164-1172.

Kim, J.-J. and J. C. M. Dekkers. 2004. A combined line-cross and halfsib model to detect and characterize QTL in an F2 outbred cross population. American Society of Animal Science Annual meeting (Abstract). http://www.fass.org/2004/abstracts/414.PDF

Kim, K.S., J. J. Kim, J. C. M. Dekkers, and M. F. Rothschild. 2004. Polar overdominant inheritance of a DLK1 polymorphism is associated with growth and fatness in pigs. Mammalian Genome 15:552-559.

Kim, K.S., J.J. Kim, J.C.M. Dekkers, and M.F. Rothschild. 2004. Polar overdominance imprinting is associated with growth and fat deposition in pigs. PAG XII p240

Kim, K.S., J.M. Reecy, W.H. Hsu, L.L. Anderson. 2004. Functional and phylogenetic analyses of a melanocortin-4 receptor mutation in domestic pigs. Domestic Animal Endocrinology 26: 75-86.

Klee EW, Carlson DF, Fahrenkrug SC, Ekker SC, Ellis LB. 2004. Identifying secretomes in people, pufferfish and pigs. Nucleic Acids Res. 32:1414-21.

Kunej T, Wu X-L, Milosevic Berlic T, Michal JJ, Jiang Z, Dovc P. 2005. Frequency distribution of a Cys430Ser polymorphism in peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) gene between Chinese and Western pig breeds. J. Anim. Breed. Genet. (in press).

Liu G, Geurts AM, Yae K, Srinivasan AR, Fahrenkrug SC, Largaespada DA, Takeda J, Horie K, Olson WK, Hackett PB. 2005. Target-site Preferences of Sleeping Beauty Transposons. J Mol Biol. 346:161-73.

Lunney, J.K. 2003. Are there immune gene alleles that determine whether a pig will be healthy? Genetics of Pig Health Symposium, Des Moines, IA. M. Boggess, Ed.; National Pork Board Press, DesMoines, IA. p.63-72.

Martínez, M.M., G.M. Hill, J.E. Link, N.E. Raney, R.J. Tempelman and C.W. Ernst. 2004. Impact of pharmacological zinc and phytase on liver metallothionein concentration and mRNA abundance in the young pig. J. Nutr. 134:538-544.

Moller M, Berg F, Riquet J, Pomp D, Archibald A, Anderson S, Feve K, Zhang Y, Rothschild MF, Milan D, Andersson L, Tuggle C 2004. High-resolution comparative mapping across pig chromocome 4 (SSC4), emphasizing the FAT1 region. Mammalian Genome 15:771-31.

Mote, B. E., J. D. Loy, M. F. Rothschild. 2004. Identification of SNPs in the insulin-like growth factor gene family and subsequent mapping of IGF2R and IGFBP1 in pigs. Plant and Animal Genome XII, Jan 10-14, San Diego, CA

Nadershahi A, Fahrenkrug SC, Ellis LB. 2004. Comparison of computational methods for identifying translation initiation sites in EST data. BMC Bioinformatics. 5:14.

Rothschild, M.F. 2004. Porcine genomics delivers new tools and results: This little piggy did more than just go to market. Genetical Research 83:1-6.

Rothschild, M.F. 2004. DNA advances offer big payoffs. Pig Progress Magazine. 20:1-3.

Rothschild, M.F. J. P. Bidanel and D.C. Ciobanu. 2004. Genome Analysis of QTL for Muscle Tissue Development and Meat Quality. In: Muscle Development of Livestock Animals. Physiology, Genetics and Muscle Quality. Eds: M.F. W. te Pas, H.P. Haagsman and M.E. Everts. CABI Publishing pgs 247-266.

Rothschild, M.F., G.S. Plastow and S. Newman. 2004. Patenting in animal breeding and genetics. In: WAAP Book of the Year 2003, Eds: A. Rosati, A. Tewolde and C. Mosconi. Pgs 269-280

Royaee AR, Husmann R, Dawson HD, Calzada-Nova G, Schnitzlein WM, Zuckermann F, Lunney JK. 2004. Deciphering the involvement of innate immune factors in the development of the host responses to PRRSV vaccination. Vet. Immunol. Immunopathol. 102: 199-216.

Smith DM, Martens GW, Lunney JK, Ando A, Lee J-H, Ho C-S, Schook L, Renard C, Chardon P. 2005. Nomenclature for Factors of the SLA Class I System, 2004. Tissue Antigens. 65: 136-149.

Stalder, K. J., M. Knauer, T. J. Baas, M. F. Rothschild, and J. W. Mabry. 2004. Sow Longevity. Pig News and Information. 25:53N-74N.

Thomsen, H., J. C. M. Dekkers, H. K. Lee, and M. F. Rothschild. 2004. Characterization of quantitative trait loci for growth and meat quality in a cross between commercial breeds of swine J. Anim. Sci. 82:2213-2228.

Tuggle, C.K., and Midwest Consortium. 2004. Finding the genes expressed in female reproductive tissues in pigs. Bulletin AS 650, January, 2004, Animal Industry Report 2004, Iowa State University, Ames, IA ASL-R1950.

Tuggle, C.K., X.W. Shi, L. Marklund, A. Stumbaugh, T.J. Stabel, M.A Mellencamp, L. Galina-Pantoja, and J. Bastiaansen 2004. Association of bacterial infection traits with genetic variation at candidate genes for porcine disease resistance. Bulletin AS 650, Animal Industry Report 2004, Iowa State University, Ames, IA ASL-R1952.

Tuggle, C.K., Y. Zhang, M.F. Rothschild, M.Moller, F. Berg, L. Anderson, J. Riquet, D. Milan, D. Pomp, A. Archibald, S. Anderson. 2004. A detailed gene map of pig chromosome 4, where the first quantitative trait locus in livestock was mapped. Bulletin AS 650, Animal Industry Report 2004, Iowa State University, Ames, IA ASL-R1951.

Walker, S. E., O.W. Robison, C.S. Whisnant, and J.P. Cassady. 2004. Effect of divergent selection for testosterone production on testicular morphology and daily sperm production in boars. Journal of Animal Science. 82: 2259-63.

Wang, C., C. Reilly, and M.S. Rutherford, 2005. A method for the comparison of cluster analyses. Statistica Sinica, in press.

Wesolowski, S.R., N.E. Raney and C.W. Ernst. 2004. Developmental changes in the fetal pig transcriptome. Physiol. Genomics. 16:268-274.

Wu X-L, Griffin KB, Garcia MD, Michal JJ, Xiao Q-J, Wright Jr. RW, Jiang Z. 2004. Census of orthologous genes and self-organizing maps (SOM) of biologically relevant transcriptional patterns in chickens (Gallus gallus). Gene 240:213-225.

Zhang, X., N. Reilly, and M.S. Rutherford, 2005. An RNA interfering system for primary porcine alveolar macrophages. Anim. Biotechnol, in press.

Zhang, X., N. Schreiber, M.P. Murtaugh, and M.S. Rutherford, 2004. Suppression of porcine reproductive and respiratory syndrome virus (PRRSV) infection by RNA-mediated gene silencing. Amer. Soc. Virol. 23rd Annual Meeting, Montreal, Canada, July 10-14.

Zhao, S.-H. A. Erickson, and C.K. Tuggle. 2004. Physical and Linkage mapping of lymphocyte antigen 86 (Ly86) gene to porcine chromosome 7. Anim. Genet. 35:164.

Zhao, S.-H. and C.K. Tuggle. 2004. Linkage mapping and expression analyses during early gestation in the pig of a novel gene, PLacentally Expressed Transcript 1 (PLET1). Anim. Genet. 35:72-74.

Zhao, S.-H., D. G. Simmons, J.C. Cross, T.E. Scheetz, T.L. Casavant, M. B. Soares, and C.K. Tuggle. 2004. PLET1, a highly expressed and processed novel gene in pig and mouse placenta is transcribed but poorly spliced in human. Genomics 84:114-125.