Amit Kishore

Identification of Appropriate Reference Genes for qRT-PCR Analysis of Heat-Stressed Mammary Epithelial Cells in Riverine Buffaloes (Bubalus bubalis)

Gene expression studies require appropriate normalization methods for proper evaluation of reference genes. To date, not many studies have been reported on the identification of suitable reference genes in buffaloes. The present study was undertaken to determine the panel of suitable reference genes in heat-stressed buffalo mammary epithelial cells (MECs). Briefly, MEC culture from buffalo mammary gland was exposed to 42 °C for one hour and subsequently allowed to recover at 37 °C for different time intervals (from 30 m to 48 h). Three different algorithms, geNorm, NormFinder, and BestKeeper softwares, were used to evaluate the stability of 16 potential reference genes from different functional classes. Our data identified RPL4, EEF1A1, and RPS23 genes to be the most appropriate reference genes that could be utilized for normalization of qPCR data in heat-stressed buffalo MECs.

Identification of suitable housekeeping genes for normalization of quantitative real‐time PCR data during different physiological stages of mammary gland in riverine buffaloes (Bubalus bubalis)

Gene expression analysis unravels the complex changes or relations at transcriptomic level. To nullify all type of errors that can be incorporated during any stage of RNA extraction into cDNA synthesis and for reliable results, the data obtained from qPCR have to be normalized using the appropriate/suitable housekeeping genes (HKGs). Unfortunately, till date, no such HKG has been reported for bubaline mammary gland. The objective of the present study was thus to identify and validate the potential HKGs for the gene expression studies in buffalo mammary gland. Mammary tissues from twelve buffaloes during different physiological stages: pre-pubertal (heifer), lactation and involution were obtained for the present study. A total of 16 potential HKGs (GAPDH, β-actin, UXT, β2M, A2M, RPl4, RPS9, RPS15A, RPS18, RPS23, HMBS, HPRT1, GTP, EEF1A1, UB1 and RPL22) from different functional classes were evaluated. The analysis revealed that the expression of EEF1A1, RPl4, β2M and RPS15A was most consistent across different physiological stages of buffalo mammary gland. On the other hand, β-actin, A2M, RPL22 and GAPDH were the least stable genes making them unsuitable as HKGs. Based on our analysis, we recommend the use of EEF1A1, RPl4, β2M and RPS15A genes as suitable HKGs for accurate normalization of gene expression data in bubaline mammary gland.

Identification of internal control genes in milk-derived mammary epithelial cells during lactation cycle of Indian zebu cow

The present study aims to evaluate the suitability of 10 candidate genes, namely GAPDH, ACTB, RPS15A, RPL4, RPS9, RPS23, HMBS, HPRT1, EEF1A1 and UBI as internal control genes (ICG) to normalize the transcriptional data of mammary epithelial cells (MEC) in Indian cows. A total of 52 MEC samples were isolated from milk of Sahiwal cows (major indigenous dairy breed of India) across different stages of lactation: Early (5-15 days), Peak (30-60 days), Mid (100-140 days) and Late (> 240 days). Three different statistical algorithms: geNorm, Normfinder and BestKeeper were used to assess the suitability of these genes. In geNorm analysis, all the genes exhibited expression stability (M) values below 0.5 with EEF1A1 and RPL4 showing the maximum expression stability. Similar to geNorm, Normfinder also identified EEF1A1 and RPL4 as two of the most stable genes. In Bestkeeper algorithm as well, all the 10 genes showed consistent expression levels. The analysis showed that four genes, that is, EEF1A1, RPL4, GAPDH and ACTB exhibited higher coefficient of correlation to the Bestkeeper index, lower coefficient of variance and standard deviation, indicating their superiority to be used as ICG. The present analysis has provided evidence that RPL4, EEF1A1, GAPDH and ACTB could probably act as most suitable genes for normalizing the transcriptional data of milk-derived mammary epithelial cells of Indian cows.

Variations in the Regulatory Region of Alpha S1-Casein Milk Protein Gene among Tropically Adapted Indian Native (Bos Indicus) Cattle.

Regulatory region of milk protein alpha S1-casein (αS1-CN) gene was sequenced, characterized, and analyzed to detect variations among 13 Indian cattle (Bos indicus) breeds. Comparative analysis of 1,587 bp region comprising promoter (1,418 bp), exon-I (53 bp), and partial intron-I (116 bp) revealed 35 nucleotide substitutions (32 within promoter region, 1 in exon-I, and 2 in partial intron-I region) and 4 Indels. Within promoter, 15 variations at positions −1399 (A > G), −1288 (G > A), −1259 (T > C), −1158 (T > C), −1016 (A > T), −941 (T > G), −778 (C > T), −610 (G > A), −536 (A > G), −521 (A > G), −330 (A > C), −214 (A > G), −205 (A > T), −206 (C > A), and −175 (A > G) were located within the potential transcription factor binding sites (TFBSs), namely, NF-κE1/c-Myc, GATA-1, GATA-1/NF-E, Oct-1/POU3F2, MEF-2/YY1, GATA-1, AP-1, POU1F1a/GR, TMF, GAL4, YY1/Oct-1, HNF-1, GRalpha/AR, GRalpha/AR, and AP-1, respectively. Seventy-four percent (26/35) of the observed SNPs were novel to Indian cattle and 11 of these novel SNPs were located within one or more TFBSs. Collectively, these might influence the binding affinity towards their respective nuclear TFs thus modulating the level of transcripts in milk and affecting overall protein composition. The study provides information on several distinct variations across indicine and taurine αS1-CN regulatory domains.

Analysis of genetic variations across regulatory and coding regions of kappa-casein gene of Indian native cattle (Bos indicus) and buffalo (Bubalus bubalis).

The promoter region of kappa-casein (κ-CN) gene in Indian native cattle and buffalo breeds was sequenced and analyzed for nucleotide variations. Sequence comparison across breeds of Indian cattle revealed a total of 7 variations in the promoter region, of which − 515 G/T, − 427 C/T, − 385 C/T, − 283 A/G and − 251 C/T were located within consensus binding sites for octamer-binding protein (OCT1)/pregnancy specific mammary nuclear factor (PMF), activator protein-2 (AP2), hepatocyte nuclear factor (HNF-1) and GAL4 transcription factors (TFs), respectively. These variations might be involved in gain or loss of potential transcription factor binding sites (TFBSs). Unlike the other 4 variants, the − 283 (A/G) variant located within HNF-1 TFBS was specific to Indian cattle as this change has not been observed in the Bos taurus sequence. Other TFBSs viz., MGF, TBP, NF-1, milk box and C/EBP were conserved across species. For the Indian native buffalo breeds, only 3 changes were identified in the promoter region; − 305 (A/C), − 160 (T/C) and − 141 (A/G) and most of the TFBSs were found to be conserved. However, deletion of two adjacent nucleotides located in and around binding site for C/EBP TF was identified in buffalo when compared with promoter sequence of bovine κ-CN. For κ-CN of Indian native cattle, a strong linkage disequilibrium (LD) was observed for variations 515 G/T, − 427 C/T and − 385 C/T in the promoter region; and for variations at codons 136 and 148 of exon-IV. Further, among intragenic haplotypes, variation − 427 C/T was found to be in LD with variations at codons 136 and 148. The information generated in the present work provides comprehensive characterization of κ-CN gene promoter and coding regions in Indian cattle and buffaloes and reported variations could become important candidates for carrying out further research in dairy traits.

Stage Specific Expression of ATP-Binding Cassette and Solute Carrier Superfamily of Transporter Genes in Mammary Gland of Riverine Buffalo (Bubalus bubalis)

In the present study, expression level of various ATP-binding cassette (ABC) viz., ABCA1, ABCA7, ABCG1, ABCG2, and ABCG5; associated transcription factors viz., SREBF1, LXRα (NR1H3), PPARA, and Solute Carriers (SLC); or Glucose transporters (GLUT) viz., SLC2A1(GLUT1), SLC2A4 (GLUT4), SLC2A8 (GLUT8), and SLC2A12 (GLUT12) superfamily of transporters were compared across physiological stages of buffalo mammary gland. The relative expression of ABCA1, and ABCG1 was significantly (p < 0.05) higher in mammary gland of heifer followed by involution and lactation stages. Similarly, ABCA7 gene expression was highest in heifer mammary gland followed by lactation and involution stages. ABCG2 gene expression was significantly (p < 0.05) high in lactating mammary gland in comparison to involution and heifer stages. On the other hand, ABCG5 gene expression was highest in involuting mammary gland followed by lactation and involution stages. Additionally, the expression of LXRα SREBF1, and PPARA which are known to regulate some of the ABC tranporters were also analyzed. The expression of LXRα gene was high in involuting as compared to lactating mammary gland. In contrast, SREBF1 and PPARA expression was significantly (p < 0.05) high in lactating mammary gland. Among the several SLC transporters studied, SLC2A1, SLC2A4, and SLC2A8 showed significant (p < 0.05) higher expression during lactation stage, whereas SLC2A12 expression was greater during heifer stage suggesting SLC2A1, SLC2A4, and SLC2A8 to be the major transporters associated with glucose uptake in buffalo mammary gland. The expression profile of (lactoferrin) LTF, known to be expressed at high level in mammary gland during involution was also studied. As expected, its expression was significantly (p < 0.05) higher during involution in comparison to lactating mammary gland.in buffaloes as well. The inclusion of LTF as a control gene further provided the confidence in the buffalo mammary gland expression data generated in the present study. This study thus helped to provide information about the distinct expression pattern of various transporters and their regulators in buffalo mammary gland during different physiological states.

Matrix‐based three‐dimensional culture of buffalo mammary epithelial cells showed higher induction of genes related to milk protein and fatty acid metabolism

Demanding transcriptomic studies in livestock animal species could be replaced by good in vitro models mimicking the function of mammary gland. Mammary epithelial cells (MEC) are the functional unit of the mammary gland. Extracellular matrix is known to be a key factor providing normal homeostasis in three‐dimensional (3D) environment as important signals are lost when cells are cultured in two‐dimensional (2D) environment. The aims of this study were to establish a buffalo mammary epithelial cells (BMECs) in 3D culture using extracellular matrix and to determine whether such a 3D culture model has different expression pattern than 2D counterpart. The purified MEC generated after several passages were used to establish 3D culture using Geltrex matrix. The expression of milk casein genes viz., alpha S1‐casein (CSN1S1), alpha S2‐casein (CSN1S2), beta‐casein (CSN2), kappa‐casein (CSN3); and fatty acid metabolism genes viz., butyrophilin (BTN1A1), glycerol‐3‐phosphate acyltransferase (GPAM), fatty acid‐binding protein 3 (FABP3), and stearoyl‐CoA desaturase (SCD) was assessed in 3D culture in comparison to traditional monolayer culture using qRT‐PCR. Notable morphological differences were observed for BMECs grown in 3D culture in comparison to 2D culture. Morphologically, epithelial structures grown in Geltrex matrix (3D) environment showed enhanced functional differentiation in comparison to 2D culture. In 3D culture, lumen and dome‐like structures were formed by day 5, whereas polarized acinus‐like structure were formed within 15 days of culturing. The expression data showed higher mRNA induction of milk casein and fatty acid metabolism genes in 10‐day‐old 3D BMECs culture in comparison to 2D monolayer culture. The result suggests that 3D organization of epithelial cells has favorable effect on induction of milk and fatty acid metabolism‐related genes. Therefore, matrix‐based 3D culture of MEC that recapitulate the structural and functional context of normal tissues could provide a better in vitro model to understand the mammary gland functioning of buffaloes.

Single Nucleotide Polymorphism in Exon 4 and Promoter Regions of ò- Lactoglobulin Gene in Native Cattle (Bos indicus) Breeds of India

The present study aims to define the distribution pattern of allelic variants in exon 4 and promoter region of β- lactoglobulin (BLG) gene in Indian native cattle (Bos indicus). PCR-RFLP analysis of exon 4 using HaeIII digestion in 968 animals of 23 Indian cattle breeds, revealed the predominance of BB genotype and B allele with an average frequency of 0.533 and 0.740, respectively. Further, comparative sequence analysis of BLG promoter region spanning 579 bp of proximal promoter region and 116 bp of exon1 revealed a total of 15 nucleotide variations with respect to Bos taurus sequence. Amongst these, variations at position -204 (C>G)/R5, widely considered to be an important site for milk protein binding factor was further screened by developing genotyping protocol using RsaI enzyme in 779 animals of Indian native cattle. Out of two alleles and three genotypes, G allele and GC genotype was found to be predominantly present with mean values of 0.639 and 0.444, respectively. Chi-square test indicated presence of genetic equilibrium in majority of the breeds with respect to studied variations and revealed no significant difference in distribution of variants across different cattle groups.