Studying the variations in differently expressed serum proteins of Hainan black goat during the breeding cycle using isobaric tags for relative and absolute quantitation (iTRAQ) technology

Abstract

The Hainan black goat is a high-quality local goat breed in Hainan Province of China. It is resistant to high temperatures, humidity, and disease. Although the meat of this breed is tender and delicious, its reproductive performance and milk yield are low. In this study, isobaric tags for relative and absolute quantitation (iTRAQ) technology was used to analyze the differentially expressed proteins in the serum of female Hainan black goats during the reproductive cycle (empty pregnant, estrus, gestation, and lactation). The pathway enrichment analysis results showed that most of the differentially expressed proteins between each period belonged to the complement and coagulation cascades. Analysis of the differential protein expression and function revealed seven proteins that were directly associated with reproduction, namely pre-SAA21, ANTXR2, vWF, SFRP3, β4GalT1, pre-IGFBP2 and Ran. This study revealed the changing patterns of differentially expressed proteins in the reproductive cycle of the Hainan black goat. pre-SAA21, ANTXR2, vWF, SFRP3, β4GalT1, pre-IGFBP2, and Ran were identified as candidate proteins for mediating the physiological state of Hainan black goats and regulating their fertility. This study elucidated the changes in expression levels of differentially expressed proteins during the reproductive cycle of Hainan black goats and also provides details about its breeding pattern.

Keywords: Cell proliferation; Hainan black goat; Isobaric tags for relative and absolute quantitation (iTRAQ) technology; Proteomics; Reproductive cycle.

Fig. 1.

Experimental flowchart.

Fig. 2.

Venn diagram of protein quantitation. Three different colors represent three biological repeats, blue represents repeat 1, red represents repeat 2, and green represents repeat 3.

Fig. 3.

Distribution of coefficient of variance (CV) in the repeated experiments. The X axis represents the CV distribution range, the Y axis represents the number of proteins in the corresponding CV range, and the right side of the figure is the number of accumulated proteins in each CV range. a~f represent the repetition test CV distribution for the four stages of the reproductive cycle: a. anestrous period-vs.-estrus period; b. anestrous period-vs.-gestation period; c. anestrous period-vs.-lactation period; d. gestation period-vs.-estrus period; e. lactation period-vs.-estrus period; f. lactation period-vs.-gestation period.

Fig. 4.

Gene oncology (GO) annotation bar chart. The histograms are GO annotations for the three GO classifications, the Y axis represents the GO entry, and the X axis represents the number of proteins annotated with the corresponding GO entry. Different colors in the figure represent different GO classifications, with red representing a biological process, green representing a cellular component, and blue representing a molecular function.

Fig. 5.

COG annotation bar chart. The Y axis represents the COG entry and the X axis represents the number of proteins annotated with the corresponding COG entry.

Fig. 6.

Significantly enriched pathway chart. The Rich Factor (RF) for the X axis represents the number of differently expressed proteins annotated to the pathway divided by the total identified proteins annotated to the pathway; and the higher the value, the greater the proportion of differently expressed proteins that are annotated to the pathway. Sizes of the dot in the figure represent the number of differently expressed proteins annotated to the pathway. a~f represent the KEGG pathway significant enrichment analysis of the differently expressed proteins during the four reproductive stages: a. anestrous period-vs.-estrus period; b. anestrous period-vs.-gestation period; c. empty pregnant phase-vs.-lactation period; d. gestation period-vs.-estrus period; e. lactation period-vs.-estrus period; f. lactation period-vs.-gestation period.