Fink Steffen, Mömke Stefanie, Distl Ottmar
Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Bünteweg 17p, 30559 Hannover, Germany.
Mol Vis. 2012;18:2229-40. Epub 2012 Aug 9.
We performed an association study for bilateral convergent strabismus with exophthalmus (BCSE) in German Brown cattle using single nucleotide polymorphisms (SNPs) located within six positional candidate genes and additional SNPs from bovine SNP databases surrounding these candidate genes. Mutation analyses included synaptotagmin 3 and 5 (SYT3, SYT5), carnitine palmitoyl-transferase 1C (CPT1C) on bovine chromosome 18 (BTA18), and plexin C1 (PLXNC1), intracellular suppressor of cytokine signaling-2 (SOCS2), and kinesin family member 21A (KIF21A) on BTA5.
For all six candidate genes, we performed cDNA analyses using eye tissues of three BCSE-affected and three unaffected controls and searched the sequences for polymorphisms. Furthermore, we screened a total of 213 SNPs on BTA5 and 136 SNPs on BTA18 from the bovine SNP databases in 29 BCSE-affected German Brown cattle and 23 breed and sex matched controls for association with BCSE. All SNPs detected within the open reading frame (ORF) of the candidate genes and all SNPs from bovine databases putatively associated with BCSE in the detection sample were genotyped in a random sample of 179 BCSE-affected German Brown cows and 161 breed and sex matched controls and tested for association with BCSE.
In total, we detected five novel SNPs within the coding sequence of the candidate genes PLXNC1 and KIF21A. The association analyses for single SNPs and haplotypes in 340 German Brown cattle revealed significant associations for five SNPs with BCSE. Four of these five SNPs were located within PLXNC1 and RDH13 and one SNP in the neighborhood of PLXNC1. Each one SNP within PLXNC1 (DN825458:c.168G>T) and RDH13 (AM930553:c.703C>A) were significantly associated with BCSE after correcting for multiple testing whereas all other SNPs failed this significance threshold. The marker-trait associations for haplotypes confirmed the significant associations with BCSE for both genes, PLXNC1 and RDH13.
The association analyses for single SNPs and haplotypes corroborated the results of the linkage study that the centromeric region of BTA5 and the telomeric end of BTA8 harbor genes responsible for BCSE. Intragenic SNPs of the genes PLXNC1 and RDH13 were experiment-wide significantly associated with BCSE and seem to play an important role in the pathogenesis of BCSE.
我们利用位于6个位置候选基因内的单核苷酸多态性（SNP）以及来自这些候选基因周围牛SNP数据库的其他SNP，对德国褐牛的双侧会聚性斜视伴眼球突出（BCSE）进行了关联研究。突变分析包括牛18号染色体（BTA18）上的突触结合蛋白3和5（SYT3、SYT5）、肉碱棕榈酰转移酶1C（CPT1C），以及BTA5上的丛状蛋白C1（PLXNC1）、细胞因子信号传导抑制因子2（SOCS2）和驱动蛋白家族成员21A（KIF21A）。
对于所有6个候选基因，我们使用3只受BCSE影响和3只未受影响对照的眼组织进行cDNA分析，并在序列中搜索多态性。此外，我们在29只受BCSE影响的德国褐牛和23只品种及性别匹配的对照中，筛选了来自牛SNP数据库的BTA5上总共213个SNP和BTA18上136个SNP与BCSE的关联。在候选基因开放阅读框（ORF）内检测到的所有SNP以及检测样本中假定与BCSE相关的来自牛数据库的所有SNP，在179只受BCSE影响的德国褐牛和161只品种及性别匹配的对照的随机样本中进行基因分型，并测试与BCSE的关联。
我们总共在候选基因PLXNC1和KIF21A的编码序列中检测到5个新的SNP。对340头德国褐牛的单SNP和单倍型的关联分析显示，5个SNP与BCSE有显著关联。这5个SNP中的4个位于PLXNC1和RDH13内，1个SNP在PLXNC1附近。在进行多重检验校正后，PLXNC1（DN825458:c.168G>T）和RDH13（AM930553:c.703C>A）内的每个SNP都与BCSE显著相关，而所有其他SNP未达到该显著性阈值。单倍型的标记-性状关联证实了PLXNC1和RDH13这两个基因与BCSE的显著关联。
单SNP和单倍型的关联分析证实了连锁研究的结果，即BTA5的着丝粒区域和BTA8的端粒末端含有导致BCSE的基因。PLXNC1和RDH13基因的基因内SNP在全实验范围内与BCSE显著相关，似乎在BCSE的发病机制中起重要作用。
