Two linked TBXT (brachyury) gene polymorphisms are associated with the tailless phenotype in fat‐rumped sheep

Abstract

Summary T‐box transcription factor T (TBXT), encoding the brachyury protein, is an embryonic nuclear transcription factor involved in mesoderm formation and differentiation. Previous studies indicate that TBXT mutations are responsible for the tailless or short‐tailed phenotype of many vertebrates. To verify whether the tailless phenotype in fat‐rumped sheep is associated with TBXT mutations, exon 2 of the TBXT gene for 301 individuals belonging to 13 Chinese and Iranian sheep breeds was directly sequenced. Meanwhile, 380 samples were used to detect the genotypes of the candidate variations by mapping to their reads databases in the Sequence Read Archive repository of GenBank. The results showed that one missense mutation, c.334G>T (GGG>TGG) with a completely linked synonymous variant c.333G>C (CCG>CCC) was found to be associated with the ‘tailless’ characteristic in typical fat‐rumped sheep breeds. The c.334G>T transversion led to the conversion of glycine to tryptophan at the 112th amino acid in the T‐box domain of the brachyury protein. In addition, crossbreeding experiments for long‐tailed and tailless sheep showed that CT/CT allele of nucleotides (nt) 333 and 334, a recessive mutation, would cause sheep tails to be shorter, suggesting that these two linked variants at nucleotides 333 and 334 in TBXT are probably causative mutations responsible for the tailless phenotype in sheep.

Trends towards revealing the genetic architecture of sheep tail patterning: Promising genes and investigatory pathways

“…Deformed vertebrae were also observed in several tailless individuals, suggesting a regulatory function of the determined mutation in tail conformation. Han et al (2019) also confirmed the Chr8:87804589G>T missense mutation in fat-rumped sheep breeds with typically fewer caudal vertebrae (Han et al 2019). The study analyzed many samples from sheep with various tail phenotypes (~681 samples obtained through direct sequencing using the point mutation region or by extracting sequencing data deposited in databases) (Han et al 2019).…”

“…(2019) also confirmed the Chr8:87804589G>T missense mutation in fat‐rumped sheep breeds with typically fewer caudal vertebrae (Han et␣al . 2019). The study analyzed many samples from sheep with various tail phenotypes (˜681 samples obtained through direct sequencing using the point mutation region or by extracting sequencing data deposited in databases) (Han et␣al .…”

“…Han et␣al . (2019) also confirmed the Chr8:87804589G>T missense mutation in fat‐rumped sheep breeds with typically fewer caudal vertebrae (Han et␣al . 2019).…”

“…The T-box transcription factor T (TBXT) gene (also known as the T gene or brachyury; chromosome 8) is a developmental transcription factor that was first discovered in mice (Herrmann et al 1990;Wilkinson et al 1990). It is involved in mesoderm formation and differentiation and regulates caudal vertebrae number and tail length in various mammalian species, including sheep (Zhi et al 2018;Han et al 2019). Zhi et al (2018) performed whole-genome sequencingbased investigation using a local Chinese sheep breed called Hulunbuir (n = 16) to reveal gene(s) and variant(s) responsible for the difference in vertebral development and tail length (Zhi et al 2018).…”

“…The study analyzed many samples from sheep with various tail phenotypes (˜681 samples obtained through direct sequencing using the point mutation region or by extracting sequencing data deposited in databases) (Han et␣al . 2019). This study also suggested a complete link between the Chr8:87804589G>T missense mutation and a neighboring synonymous mutation (Chr8:87804590G>C; Oar_v3.1; c.G333C).…”