Microtia and anotia are hereditary traits characterized by an underdevelopment or complete absence of the outer ear. These congenital malformations observed in many species can exist as part of various syndromes or as an isolated trait as seen in the fat-tailed Awassi sheep breed. Our study aims to identify the genetic mutations causing microtia in Awassi sheep by DNA sequencing. DNA was extracted from blood samples randomly collected from 84 Awassi sheep (16 earless, 41 short ear and 27 normal ear) across different farms. GATA6 exons 1, 2, 4, 6 and 7, CLRN1 intron 3, DCC intron 2, ECR near HMX1 and the intergenic region between GATA6 and MIB1 genes were screened, amplified and sequenced. Allele and genotype frequencies were calculated by direct counting. Association was performed using chi-squared test for goodness-of-fit. Results showed mutations in only two genes significantly associated with microtia in Awassi: duplication in part of ECR near HMX1 (6:114293121-6:114293196) and a SNP at GATA6 exon 7 (23:34498242). Association results revealed that the ECR locus accounts for the microtia phenotype, while GATA6 exon 7 acts as a modifier gene. Genetic screening for these loci can be used to improve selection against microtia in Awassi sheep.

中文翻译：

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ECR 中 HMX1 附近的重复和 GATA6 基因中的 S​​NP 调节 Awassi 绵羊的小耳畸形

Microtia 和 annotia 是遗传特征，其特征是外耳发育不全或完全缺失。在许多物种中观察到的这些先天性畸形可以作为各种综合征的一部分或作为孤立的特征存在，如在肥尾 Awassi 绵羊品种中所见。我们的研究旨在通过 DNA 测序鉴定导致 Awassi 绵羊小耳畸形的基因突变。从不同农场的 84 只 Awassi 羊（16 只无耳、41 只短耳和 27 只正常耳）随机采集的血液样本中提取 DNA。GATA6 外显子 1、2、4、6 和 7、CLRN1 内含子 3、DCC 内含子 2、HMX1 附近的 ECR 以及 GATA6 和 MIB1 基因之间的基因间区域被筛选、扩增和测序。通过直接计数计算等位基因和基因型频率。使用卡方检验进行拟合优度关联。结果显示只有两个基因的突变与 Awassi 的小耳畸形显着相关：HMX1 附近的部分 ECR 重复 (6:114293121-6:114293196) 和 GATA6 外显子 7 的 SNP (23:34498242)。关联结果显示，ECR 基因座解释了小耳畸形表型，而 GATA6 外显子 7 作为修饰基因。这些基因座的遗传筛选可用于改进对 Awassi 绵羊中小耳畸形的选择。