DNA fingerprinting analysis of Booroola pedigrees: a search for linkage to the Booroola gene

Seven minisatellite probes from a variety of sources were used to analyse 11 paternal half-sib families in which the Booroola gene was segregating. A total of 402 bands that showed segregation in the pedigrees were examined for linkage to the Booroola gene. None of the bands showed segregation with the Booroola gene. The most likely evidence for a linked band was produced by the HaRas HVR probe in Family 902 (=0.0; LOD 2.3). The conclusion, however, is that the minisatellite probes used in this study could not be used as markers for the Booroola gene. The study highlighted problems associated with the use of minisatellite probes in linkage studies in half-sib families. The complex banding patterns found on fingerprinting gels was a major source of scoring error. In a few cases both of the sire's alleles could be identified at a particular locus, but in most cases only one of the alleles could be identified. For the most part, the bands had to be treated as dominant alleles. The contribution of dam alleles to the banding pattern could only be estimated. There was an indication that minisatellite loci in sheep are clustered in particular regions of the sheep genome as the rate at which bands segregated with each other was higher than one would expect from loci randomly distributed throughout the genome.     

Highly prolific Booroola sheep have a mutation in the intracellular kinase domain of bone morphogenetic protein IB receptor (ALK-6) that is expressed in both oocytes and granulosa cells

The Booroola fecundity gene (FecB) increases ovulation rate and litter size in sheep and is inherited as a single autosomal locus. The effect of FecB is additive for ovulation rate (increasing by about 1.6 corpora lutea per cycle for each copy) and has been mapped to sheep chromosome 6q23-31, which is syntenic to human chromosome 4q21-25. Bone morphogenetic protein IB (BMP-IB) receptor (also known as ALK-6), which binds members of the transforming growth factor-beta (TGF-beta) superfamily, is located in the region containing the FecB locus. Booroola sheep have a mutation (Q249R) in the highly conserved intracellular kinase signaling domain of the BMP-IB receptor. The mutation segregated with the FecB phenotype in the Booroola backcross and half-sib flocks of sheep with no recombinants. The mutation was not found in individuals from a number of sheep breeds not derived from the Booroola strain. BMPR-IB was expressed in the ovary and in situ hybridization revealed its specific location to the oocyte and the granulosa cell. Expression of mRNA encoding the BMP type II receptor was widespread throughout the ovary. The mutation in BMPR-IB found in Booroola sheep is the second reported defect in a gene from the TGF-beta pathway affecting fertility in sheep following the recent discovery of mutations in the growth factor, GDF9b/BMP15.     

Genes encoding the alpha and beta chains of follicle-stimulating hormone are not sites for the Booroola (FecB) mutation in sheep.

Bovine cDNA probes for the beta-subunit of follicle-stimulating hormone beta (FSH beta) and the alpha-subunit of the glycoprotein hormones identify genetic variation (polymorphic restriction fragments) near these genes in sheep. The inheritance of the polymorphic restriction fragments was studied in half-sibling pedigrees generated by mating heterozygous (B+) rams to non-carrier (++) ewes so that the co-inheritance or genetic linkage to the Booroola (FecB) locus and the alpha- and beta-subunits of FSH could be analysed. Genetic recombination was observed between the FSH beta locus and the FecB locus in all five families studied and between the alpha-subunit and the FecB locus in the two families studied. We conclude that the FecB mutation does not lie within the FSH beta- or alpha-subunit genes encoding the heterodimeric hormone FSH, and that the high concentrations of FSH observed in carrier ewes must result from indirect actions of the FecB mutation on the synthesis, processing, storage, release or metabolism of FSH.     

Infantile hypophosphatasia--linkage with the RH locus

Linkage analysis of six nuclear families with infantile hypophosphatasia which were informative for the Rh blood group locus was performed. The maximum combined lod score was 4.76 with the recombinant distance (theta) of 0.04. These preliminary data provide evidence for linkage between the genes for infantile hypophosphatasia and the Rh blood group and provisionally assign the gene locus for infantile hypophosphatasia (designated HOPS) to chromosome 1p.     

The genetic relationship between the Hbb locus and body size in a population of mice divergently selected for six-week body weight.

Both pleiotropy and linkage were examined as possible explanations for the fixation of the Hbb3 allele in the six Large lines of a population of mice divergently selected for six-week body weight (six replicates in each direction and six controls). A survey of over 1200 individuals in the lines still segregating at the Hbb locus excluded pleiotropy as a possible explanation. The results showed a nonsignificant effect of haemoglobin genotype on body weight. The linkage relationship of the Hbb locus was examined using a backcross mating system. The Hbb3 c+ region (chromosome 7) of a Large line was backcrossed into its corresponding Small line (Hbb4 c). The resultant difference in body weight between the two segregants (Hbb8 c+ [Hbb4 c; Hbb4 c/Hbb4 c) was measured. The results suggested linkage as the most plausible explanation for the fixation of the Hbb4 allele in the six Large lines.     

绵羊微卫星BMS2508和FecB基因的多态及连锁分析

文章分析与绵羊高繁殖力主效基因FecB紧密连锁的微卫星座位BMS2508在高繁殖力绵羊品种(小尾寒羊)和低繁殖力绵羊品种(特克塞尔、多赛特和中国美利奴)中的遗传多态性, 同时探讨该微卫星座位与小尾寒羊FecB基因的连锁不平衡关系。高繁殖力品种小尾寒羊在骨形态发生蛋白受体IB(Bone morphogenetic protein receptor IB, BMPR-IB)基因编码序列第746位碱基处发生了与Booroola Merino绵羊相同的FecB突变(A746G), 而在低繁殖力的特克塞尔、多赛特和中国美利奴绵羊中没有检测到该突变; 小尾寒羊BB、B+、++的基因型频率分别为0.485、0.398和0.117。微卫星座位BMS2508在4个绵羊品种的438个个体中共检测到8个等位基因和15种基因型, 最小等位基因为94 bp, 最大等位基因为116 bp; 小尾寒羊(n = 307)、特克塞尔(n = 45)、多赛特(n = 46)、中国美利奴(n = 40)和BB型(n = 149)、B+型(n = 122)、++型(n = 36)小尾寒羊群体中优势等位基因分别是100 bp、94 bp、94 bp、112 bp、100 bp、100 bp、112 bp, 其频率分别为0.453、0.544、0.802、0.475、0.483、0.439、0.389。连锁不平衡分析显示小尾寒羊FecB基因B等位基因与BMS2508微卫星座位100 bp等位基因之间存在一定的连锁不平衡(D′=0.408), 而+等位基因与BMS2508微卫星座位110 bp和114b p等位基因均存在一定的连锁不平衡(D′=0.513)。     

Genetic linkage analysis between protein polymorphisms and the FecB major gene in sheep

A genetically linked marker locus is sought for the Booroola gene (FecB), a major gene which confers increased prolificacy in sheep. We examined 18 polymorphic proteins in sheep and found 10 to be informative in half-sib families where the Booroola gene was segregating. Recombination was observed between each of the protein loci and the Booroola gene. The loci and exclusion distance for each (calculated as the recombination fraction where the lod score was equal to -2.0) are as follows: NADH diaphorase, DIA1 (9.2 cM); arylesterase, EsA (11.9 cM); haemoglobin beta chain, HBB (17.5 cM); leucine amino peptidase, LAP (19.7 cM); malic enzyme, ME1 (14.8 cM); ovine plasminogen antigen, OPA (12.6 cM); alpha-1-protease inhibitor, PI2 (5.7 cM), erythrocyte 'X' protein, Prot-X (25.3 cM); post transferrin, PTF (2.2 cM); transferrin, TF (33.8 cM).     

Linkage relationships among 20 genetic markers in cattle. Evidence for linkage between two pairs of blood group systems: B-Z and S-F/V respectively

Five bovine paternal half-sib pedigrees for a total of 527 individuals were typed for six blood group systems: A, B, F/V, L, S, Z; for nine biochemical polymorphisms: ADA, MPI, PGM-3(slow), NP, Gc, Pi2, Tf, Ptf1 and Ptf2; and for restriction fragment length polymorphisms at five autosomal loci: Tg, GH, LDLr, BoLA-DQ and BoLA-DY. Two of the pedigrees were informative for segregation at the 'muscular hypertrophy' locus, and one was informative at the coat colour determining 'roan' locus. Linkage analysis was performed between all markers. Linkage was demonstrated between the S and F/V blood group systems (z = 3.11), adding one locus to the previously identified linkage group VII (LGVII) [Pi-2 and S], the most likely order being Pi2-S-F/V with maximum likelihood recombination rates of 0.208 and 0.211. Also shown to be linked were the blood group systems B and Z (z = 5.7, theta = 0.245). We confirmed the observation previously made by Andersson et al. (1988) of a high recombination rate between class II genes DQ and DY, suggesting either a larger physical distance between those genes than expected from comparative data, or the presence of a 'recombinational hotspot' in the bovine major histocompatibility complex. No linkage was found either with the 'muscular hypertrophy' locus, or with the 'roan' locus. However, these two loci could be excluded from respectively 1.7 and 2.5 Morgans of the bovine genome.     

Fec基因及BMPR-IB基因的突变特性与生物学意义

FecB基因位于Booroola绵羊的常染色体上,具有提高排卵率和产羔数等生物学作用。FecB基因已被定位在绵羊6号染色体6q23~q31的狭窄区域内,并且已从分子水平上找到了控制Booroola绵羊排卵数的主效基因。本文详细阐述了近年来对FecB基因的定位及分子生物学作用机制方面的研究进展。     

Genome-wide association mapping of blood cell traits in mice

Genetic variations in blood cell parameters can impact clinical traits. We report here the mapping of blood cell traits in a panel of 100 inbred strains of mice of the Hybrid Mouse Diversity Panel (HMDP) using genome-wide association (GWA). We replicated a locus previously identified in using linkage analysis in several genetic crosses for mean corpuscular volume (MCV) and a number of other red blood cell traits on distal chromosome 7. Our peak for SNP association to MCV occurred in a linkage disequilibrium (LD) block spanning from 109.38 to 111.75 Mb that includes Hbb-b1, the likely causal gene. Altogether, we identified five loci controlling red blood cell traits (on chromosomes 1, 7, 11, 12, and 16), and four of these correspond to loci for red blood cell traits reported in a recent human GWA study. For white blood cells, including granulocytes, monocytes, and lymphocytes, a total of six significant loci were identified on chromosomes 1, 6, 8, 11, 12, and 15. An average of ten candidate genes were found at each locus and those were prioritized by examining functional variants in the HMDP such as missense and expression variants. These results provide intermediate phenotypes and candidate loci for genetic studies of atherosclerosis and cancer as well as inflammatory and immune disorders in mice.     

Genetic variation at a pig serum protein locus, Po-2 and its assignment to the Phi, Hal, S, H, Pgd linkage group

Two-dimensional agarose gel (pH 5.4)-polyacrylamide gel (pH 9.0) electropho-resis of pig serum samples revealed a new serum protein (postalbumin-2, PO-2) polymorphism. Family data supported the hypothesis that the three PO-2 phenotypes observed were controlled by two codominant, autosomal alleles ( Po-2^F and Po-2^S ) at a single locus. The frequency of Po-2^F in Swedish Landrace and in Swedish Yorkshire breeds was estimated at 0.74 and 0.65, respectively. Evidence was presented for close genetic linkage between Po-2 and the red cell phospho-hexose isomerase locus ( Phi ). A recombination frequency of 3.2 % was obtained from double backcross material. Data obtained in a Danish Landrace material showing linkage between the Po-2 locus and the H blood group locus, the Pgd locus and Hal (locus for halothane sensitivity) are also given. A total of seven re-combinants were observed. They show that Po-2 is a new locus in a previously established linkage group. The likely sequence of the loci is: Phi, Hal, S, H, Po-2, Pgd .     

Linkage analyses of multiple endocrine neoplasia, type 2A (MEN-2A) with 20 DNA polymorphisms: 5% of the genome excluded

Pairwise linkage analyses are reported between the locus for multiple endocrine neoplasia type 2A (MEN-2A) and 20 restriction fragment length polymorphisms (RFLPs) in a single large kindred which was previously screened for linkage with this form of cancer using 23 blood group and serum protein polymorphisms. No significant, positive lod scores have been obtained so far. These 20 RFLPs have excluded the MEN2 locus from about as much of the genome as did the 23 classical markers previously reported. This is a clear demonstration of the value of RFLPs for linkage studies since these 20 RFLPs were not selected for being the most polymorphic of those available. Over 10% of the human genome has been excluded from linkage with the MEN2 locus in this particular family.     

Genetic markers for the Booroola fecundity (Fec) gene in sheep

Animals from the Booroola line of Australian Merino sheep are characterized by a high ovulation rate that can be attributed to the presence of a codominant allele (Fec ^B).The specific function of the gene has not been identified. Effective use of the trait within the sheep breeding industry requires one or more genetic markers that can distinguish between alternative alleles at the locus Fec. With a combination of DNA minisatellite markers and polymorphic protein markers, a cluster of seven minisatellite fragments has been identified as being linked to the Fec gene and to the ovine A blood group locus. The minisatellite fragments have been derived from multilocus probes and hence cannot be used to define the chromosomal location of the Fec gene or to serve as diagnostic markers for Fec. The derivation of cloned single locus markers from the minisatellite fragments will enable finer scale mapping of the Fec and the A blood group locus in sheep.     

Multilocus genetic determinants of LDL particle size in coronary artery disease families.

Recent interest in atherosclerosis has focused on the genetic determinants of low-density lipoprotein (LDL) particle size, because of (i) the association of small dense LDL particles with a three-fold increased risk for coronary artery disease (CAD) and (ii) the recent report of linkage of the trait to the LDL receptor (chromosome 19). By utilizing nonparametric quantitative sib-pair and relative-pair analysis methods in CAD families, we tested for linkage of a gene or genes controlling LDL particle sizes with the genetic loci for the major apolipoproteins and enzymes participating in lipoprotein metabolism. We confirmed evidence for linkage to the LDL receptor locus (P=.008). For six candidate gene loci, including apolipoprotein(apo)B, apoAII, apo(a), apoE-CI-CII, lipoprotein lipase, and high-density lipoprotein-binding protein, no evidence for linkage was observed by sib-pair linkage analyses (P values ranged from .24 to .81). However, in addition, we did find tentative evidence for linkage with the apoAI-CIII-AIV locus (chromosome 11) (P=.06) and significant evidence for linkage of the cholesteryl ester transfer protein locus (chromosome 16) (P=.01) and the manganese superoxide dismutase locus (chromosome 6) (P=.001), thus indicating multilocus determination of this atherogenic trait.     

The half-life of follicle-stimulating hormone in ovary-intact and ovariectomized booroola and control merino ewes

To determine whether the high ovulation rate of the Booroola Merino ewe could be explained by FSH metabolism we have tested the proposition that FSH may have a longer half-life in the plasma of Booroola Merino ewes than in control ewes. The half-life of plasma FSH was determined by removal of the pituitary gland, to abolish FSH secretion into the peripheral circulation, and monitoring by repeated blood sampling the subsequent decline in plasma FSH concentrations. The half-life of FSH was similar in Booroola (103 +/- 14 (s.e.m.) min, N = 8) and control (116 +/- 8 min, N = 9) ewes. However, when ewes that had been ovariectomized at least 6 months earlier were hypophysectomized, the half-life of FSH was increased from 110 + 8 min in ovary-intact ewes (N = 11) to 1101 +/- 49 min (N = 6) (P less than 0.001) with no difference between the two Merino strains. We conclude that changes in the circulating half-life of FSH do not account for the high fecundity of the Booroola but that ovariectomy can alter the half-life of FSH secreted by the pituitary gland.     

四引物扩增受阻突变体系PCR快速测定绵羊 BMPR-IB基因型方法的建立

四引物ARMS PCR是检测SNP有效、快速、简便的方法.绵羊BMPR-lB基因是控制Booroola绵羊多胎性状的主效基因,此研究目的在于建立一种对BMPR-IB基因四引物ARMS PCR检测方法.根据四引物ARMS PCR技术原理,在绵羊BMPR-IB基因突变位点(A746G)设计一对特异性引物,并在突变点两侧设计一对参照引物,用来扩增含有突变点的DNA片段,可在一步PCR反应中根据电泳图谱准确判断绵羊个体的BMPR-IB基因型,对比PCR-RFLP检测结果表明,所建立的方法简单,操作简便,大大提高了检测效率.     

Linkage disequilibrium between the ELA and the A blood group systems in Standardbred horses

The linkage group formed by the ELA and A blood group system in horses was studied in American Standardbred horses. The distance between the ELA locus and the A blood group locus was measured as 1.61 centimorgans. observing only the haplotypes contributed by the sires.
Strong linkage disequilibrium was found in pacing Standardbred horses for ELA-W1 with Aa, ELA-W5 with Ab and ELA-W10 with Ab. Linkage disequilibrium was apparent at both the population and family level. Among trotting Standardbred horses, linkage disequilibrium was found for ELA-W1 with Aa and for ELA-W10 with Ab. It was not possible to investigate linkage relationships in Thoroughbred horses because of the high frequency of Aa and low frequency of other A system markers.     

An RFLP linkage map for loblolly pine based on a three-generation outbred pedigree

A genetic linkage map for loblolly pine (Pinus taeda L.) was constructed using segregation data from a three-generation outbred pedigree consisting of four grandparents, two parents, and 95 F₂ progeny. The map was based predominantly on restriction fragment length polymorphism (RFLP) loci detected by cDNA probes. Sixty-five cDNA and three genomic DNA probes revealed 90 RFLP loci. Six polymorphic isozyme loci were also scored. One-fourth (24%) of the cDNA probes detected more than 1 segregating locus, an indication that multigene families are common in pines. As many as six alleles were observed at a single segregating locus among grandparents and it was not unusual for the progeny to segregate for three or four alleles per locus. Multipoint linkage analysis placed 73 RFLP and 2 isozyme loci into 20 linkage groups; the remaining 17 RFLP and 4 isozyme loci were unlinked. The mapped RFLP probes provide a new set of codominant markers for genetic analyses in loblolly pine.     

Genetic linkage between the loci for phosphohexose isomerase (PHI) and a serum protein (Xk) in horses

Genetic linkage between the equine loci for phosphohexose isomerase (PHI) and serum Xk protein was demonstrated by means of segregation data from three sire families. The recombination frequency was estimated from pooled data to be 0.23 +/- 0.02; a significant heterogeneity between sires for estimates of the recombination frequency was observed. No indication of linkage was detected between Xk and 14 other blood marker loci. Linkage between the Xk locus and the locus for soluble malic enzyme (ME1) has recently been reported in horses. An equine linkage group designated LG IV comprising the three loci ME1, PHI, and Xk has thus been established. The possibility that the linkage between PHI and Xk is homologous to the linkage between the loci for PHI and a serum postalbumin (PO-2) in pigs was discussed.     

Serologically defined specificities of the pig main histocompatibility complex (SL-A)

Six antigens detectable by the complement-dependent lymphocytotoxic technique were determined in pigs by six groups of alloimmune sera. It was confirmed that these specificities are controlled by the main histocompatibility region (SL-A). Serological and genetic studies showed that the given specificities (provisionally designated LI to L6) form at least 6 haplotypes. In addition, family studies confirmed the linkage between SL-A region and C blood group locus. Maximum lod score values are in recombination fraction v = 0.2.