Nonneman Dan J, Wise Tommy H, Ford J Joe, Kuehn Larry A, Rohrer Gary A
USDA-ARS, US Meat Animal Research Center, Clay Center, Nebraska, 68933, USA.
BMC Vet Res. 2006 Sep 13;2:28. doi: 10.1186/1746-6148-2-28.
The rate of pubertal development and weaning to estrus interval are correlated and affect reproductive efficiency of swine. Quantitative trait loci (QTL) for age of puberty, nipple number and ovulation rate have been identified in Meishan crosses on pig chromosome 10q (SSC10) near the telomere, which is homologous to human chromosome 10p15 and contains an aldo-keto reductase (AKR) gene cluster with at least six family members. AKRs are tissue-specific hydroxysteroid dehydrogenases that interconvert weak steroid hormones to their more potent counterparts and regulate processes involved in development, homeostasis and reproduction. Because of their location in the swine genome and their implication in reproductive physiology, this gene cluster was characterized and evaluated for effects on reproductive traits in swine.
Screening the porcine CHORI-242 BAC library with a full-length AKR1C4 cDNA identified 7 positive clones and sample sequencing of 5 BAC clones revealed 5 distinct AKR1C genes (AKR1CL2 and AKR1C1 through 4), which mapped to 126-128 cM on SSC10. Using the IMpRH7000rad and IMNpRH212000rad radiation hybrid panels, these 5 genes mapped between microsatellite markers SWR67 and SW2067. Comparison of sequence data with the porcine BAC fingerprint map show that the cluster of genes resides in a 300 kb region. Twelve SNPs were genotyped in gilts observed for age at first estrus and ovulation rate from the F8 and F10 generations of one-quarter Meishan descendants of the USMARC resource population. Age at puberty, nipple number and ovulation rate data were analyzed for association with genotypes by MTDFREML using an animal model. One SNP, a phenylalanine to isoleucine substitution in AKR1C2, was associated with age of puberty (p = 0.07) and possibly ovulation rate (p = 0.102). Two SNP in AKR1C4 were significantly associated with nipple number (p </= 0.03) and another possibly associated with age at puberty (p = 0.09).
AKR1C genotypes were associated with nipple number as well as possible effects on age at puberty and ovulation rate. The estimated effects of AKR1C genotypes on these traits suggest that the SNPs are in incomplete linkage disequilibrium with the causal mutations that affect reproductive traits in swine. Further investigations are necessary to identify these mutations and understand how these AKR1C genes affect these important reproductive traits. The nucleotide sequence data reported have been submitted to GenBank and assigned accession numbers [GenBank:DQ474064-DQ474068, GenBank:DQ494488-DQ494490 and GenBank:DQ487182-DQ487184].
青春期发育速率与断奶至发情间隔相关，且影响猪的繁殖效率。在猪10号染色体（SSC10）端粒附近的梅山杂交猪中已鉴定出青春期年龄、乳头数和排卵率的数量性状基因座（QTL），该区域与人类10号染色体p15同源，包含一个醛糖还原酶（AKR）基因簇，至少有六个家族成员。AKR是组织特异性羟类固醇脱氢酶，可将弱类固醇激素转化为其更强效的对应物，并调节参与发育、体内平衡和繁殖的过程。由于它们在猪基因组中的位置及其在生殖生理学中的意义，对该基因簇进行了表征并评估其对猪繁殖性状的影响。
用全长AKR1C4 cDNA筛选猪CHORI - 242 BAC文库，鉴定出7个阳性克隆，对5个BAC克隆进行样本测序，发现5个不同的AKR1C基因（AKR1CL2和AKR1C1至4），它们定位于SSC10上的126 - 128 cM。使用IMpRH7000rad和IMNpRH212000rad辐射杂种板，这5个基因定位于微卫星标记SWR67和SW2067之间。将序列数据与猪BAC指纹图谱进行比较，表明基因簇位于300 kb区域。对美国肉类动物研究中心（USMARC）资源群体四分之一梅山后代F8和F10代的初情期年龄和排卵率的后备母猪进行12个单核苷酸多态性（SNP）基因分型。使用动物模型通过MTDFREML分析青春期年龄、乳头数和排卵率数据与基因型的关联。一个SNP，即AKR1C2中苯丙氨酸到异亮氨酸的取代，与青春期年龄相关（p = 0.07），可能与排卵率也相关（p = 0.102）。AKR1C4中的两个SNP与乳头数显著相关（p≤0.03），另一个可能与青春期年龄相关（p = 0.09）。
AKR1C基因型与乳头数相关，也可能对青春期年龄和排卵率有影响。AKR1C基因型对这些性状的估计影响表明，这些SNP与影响猪繁殖性状的因果突变处于不完全连锁不平衡状态。有必要进一步研究以鉴定这些突变，并了解这些AKR1C基因如何影响这些重要的繁殖性状。所报道的核苷酸序列数据已提交至GenBank，并被赋予登录号[GenBank:DQ474064 - DQ474068，GenBank:DQ494488 - DQ494490和GenBank:DQ487182 - DQ487184]。
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