Prevalence of the Beta Case in Variants Among Tharparkar, Rathi, Sahiwal, Kankrej and Cross Breed and Its Influence Under Selective Pressure
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Int.J.Curr.Microbiol.App.Sci (2019) 8(3): 1842-1848 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 8 Number 03 (2019) Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2019.803.218 Prevalence of the Beta Case in Variants among Tharparkar, Rathi, Sahiwal, Kankrej and Cross Breed and its Influence under Selective Pressure Mrinalini Saran1*, Ankita Gurao1, Rajeev Kumar Joshi2 and S.K. Kashyap1 1Department of Veterinary Microbiology and Biotechnology, 2Department of Animal Genetics and Breeding, RAJUVAS, Bikaner, India *Corresponding author ABSTRACT Milk has been regarded as wholesome food since centuries. The major milk proteins are K e yw or ds the casein (80%) and the whey proteins (10%). One of the prominent milk proteins in cattle i.e. beta casein, is encoded by highly polymorphic genes, leading to formation of 12 Beta-casein, A2 type milk, Cross- protein variants. Among them A1 and A2 variant are the most frequent; the A2 being the bred, Bos indicus primitive type present in Bos indicus at higher percentage than Bos taurus. Most of the indicine cattle breed is A2 type carrying presence of histidine in A1 in contrast to proline Article Info in A2 makes it susceptible to gastrointestinal proteolysis digestion to release beta- casomorphin-7 (BCM-7), which has been implicated in various human health ailments. Accept ed: 15 February 2019 The following study has been conducted to concisely predict the diminishing percent of A2 Available Online: allele in the cross -bred Rathi cattle herd in compared to the pure-bred Rathi and other 10 March 2019 indigenous cattle and evaluate the change in A2 allele frequency in course of generations. Introduction population. The world per capita milk availability was 322 gm/day (3) during 2014- Milk has been regarded as a wholesome food 15. Like any other developing country, the and also an essential part of diet for both fluid milk consumption of India is higher than infants and adults. Worldwide the major world average, thus again indicating the sources of milk are cow, buffalo, goat, sheep necessity to focus on milk consumption and camel, contributing 85%, 11%, 2%, 1.4% related health aspects. and 0.2% of world milk production respectively. Cow contributes highest to the The widely consumed cow milk has protein milk production i.e. 600 million tonnes (83% content ~32 g/l, that forms the major portion of total milk produced) (1) of milk every year of protein in diet of infants and lacto- and with a herd capacity of total 264 million vegetarians next to the legumes. The casein worldwide (1). The total milk production in (80%) is abundant among the protein fraction, India is highest in the world, approximately comprising α-casein (29%), β-casein (27%) 182.16 million tonnes (2), 178 million cattle and κ-casein (10%). The gene coding for 1842 Int.J.Curr.Microbiol.App.Sci (2019) 8(3): 1842-1848 CSN2 gene (β-casein) is present on BTA-6. breed). Whereas the indicine cattle have Like all other milk proteins, beta -casein is evolved naturally without any selection highly polymorphic. Total of 49 milk protein pressure; thus, allowing them to carry higher variants have been reported by Farell et al., frequency of A2 allele. The consumption of 2004. Till now 12 genetic variants (A1, A2, the A1 type milk in European population has A3, B, C, D, E, F, H1, H2, I, G) have been been clearly associated with type I diabetes reported for beta casein(4). The most common (9,10,12,), ischemic heart disease (12,10) and form of beta casein in dairy cattle breeds are neurological disorders (13) by several A1 and A2, while B is less common and A3, C epidemiological data. The following are rare (5). On the basis of their potential to investigation has been done to estimate the release beta casomorphin-7, beta casein diminishing A2 allele frequency among the variants can be categorized as A1 type and A2 indigenous cattle and cross-bred Rathi cattle in type, the previous one containing B,C,F,G and compared to the pure bred indigenous Rathi D variants, whereas the later category contains breed. This will aid in planning the breeding A3, E, D, H1, H2 and I (6). Among all the policies in future, so that the A2 gene pool mutations occuring on beta casein, at 67th remain conserved in the indigenous herd. position of the protein a noteworthy mutation has lead to replacement of proline by histidine. Materials and Methods The codon CCT (proline) was replaced by CAT (histidine) leading to formation of For the purpose of this work, Rathi pure breed, variant A2 and A1 respectively. Presence of Sahiwal, Kankrej, Tharparkar and cross breed histidine at A1 in contrast to proline in A2 (Rathi×Holstein Fresian) were obtained from makes it susceptible to gastrointestinal LRS (CVAS, Rajasthan University of proteolytic digestion for releasing beta- Veterinary and Animal Sciences, Bikaner), casomorphin-7 (BCM-7), which has been LRS (Kodamdesar, Bikaner), LRS (Beechwal, implicated in not only the type I diabetes and Bikaner) and LRS (CVAS, Rajasthan IHD (Ischaemic Heart Diseases) but also in University of Veterinary and Animal Sciences, several other non communicable diseases like Bikaner)., All the cattle were free of mastitis SIDS (Sudden Infant Death Syndrome), and blood was collected from juglar veins and schizophrenia, autism, milk related allergies genomic DNA was extracted on the same day (7) and arteriosclerosis (8). The using QIAamp® DNA mini kit (Qiagen). The epidemiological, in vivo and in vitro studies DNA was then taken for purity and have concluded with both positive (9,10) and concentration check by the use of nanodrop negative correlation (11) of the A1/A2 milk device. consumption to the alleged health issues., This mutation also carry an evolutionary The ACRS-PCR and PCR-RFLP was significance, the A2 being the primitive type performed using the primers described by Lien present in Bos indicus at higher percentage et al., (1992) and McLachlan (2006) than Bos taurus. The majority of taurine respectively (14,15). breeds domesticated in America, Europe and Australia (excluding Indian sub-continent, CASB67: 5’-CCTGCAGAATTCTAGTCTA most of the African zebu and few Far-East TCCCTTCCCTGGGCCCATCG-3’ countries) are taurine which has been bred CASB122:5’-GAGTCGACTGCAGATTT selectively for higher milk production, leading TCAACATCAGTGAGAGTCAGGCCCTG- to lower frequency of A2 allele (few 3’ exceptions e.g. Guernsey and Fleckvieh 1843 Int.J.Curr.Microbiol.App.Sci (2019) 8(3): 1842-1848 Csn4F: 5’-CCTTCTTTCCAGGATGAACTC Rathi were amplified using the ACRS-PCR CAGG-3’ and PCR-RFLP primers (Fig. 1(A) and Fig.1(B)) and digested using TaqI and DdeI Csndde4R: 5’-GAGTAAGAGGAGGGATGT enzyme (Fig. 2 and 3) respectively. The TTTGTGGGAGGCTCT-3’ resultant RFLP pattern from TaqI was interfered to distinguish A1A1 genotype (213 The primers CASB67 and CASB122 have bp), A2A2 genotype (251 bp) and A1A2 been designed in such a way that so that upon genotype (251 and 213 bp). Whereas the DdeI amplification a restriction site for a taqI was interfered to distinguish A1A1 genotype enzyme is created in the amplicon. The (121 bp), A2A2 genotype (86, 35 bp) and primers (csn4F and csnDde4R) are designed to A1A2 genotype (121, 86, 35 bp). All the cattle amplify the beta casein’s exon 7th and of Tharparkar, Rathi and Kankrej breed amplified product has the naturally occuring displayed single band of 251 bp, indicating restriction site for DdeI enzyme. The PCR- toward the A2A2 genotype on digestion with RFLP was only used for amplifying Sahiwal TaqI enzyme. Out of the 30 Sahiwal, 4 DNA. The PCR was performed by 200 ng of showed dual bands of 121 bp and 86 bp, genomic DNA in a 25 μl reaction volume therefore indicating toward the A1A2 containing final volume of 5 pmol of primers, genotype (Fig.3 (A)). 10 samples of Rathi 200 μM of each dNTP and 1 U of Taq cross bred (Rathi× Holstein Fresian) cattle polymerase (GoTaq® PCR Core System I examined with the DdeI which displayed only Promega). The PCR cycles were as follows- two bands of 86 and 35 bps, indicating them to 95oC for 5 min, and 30 cycles of 94oC for 1 be carrying A2A2 genotype (Fig.3 (B)). To min, 62oC for 45 sec, 72oC for 30 sec and final determine the SNP at 875287 (90th position on extension of 7 min. For Csn 4F/ 4R primer 6th chromosome that is comprised within 7th pair the annealing temperature was of 580C for exon of beta casein gene, we sequenced the 30 sec. The PCR was run on 2% agarose gel at samples that exceptionally displayed A1 100 V for 1 hour to detect the product size of allele. The sequencing results suggest 251bp and 121 bp for CASB67/122 (Fig no. occurrence of C to A allele change. 1(A)) and Csn4F/Dde4R (Fig no. 1(B)). The final product was cleaved in a 25μl reaction The mean allele frequency of A1 allele in Bos involving 15μl of PCR product, 2.5μl of 10× indicus has been reported as 0.98 (15), where NEB cutsmart buffer, 5U of TaqI enzyme for in the present study has came with an CASB67/122 primer product and 5U of DdeI unexpected A2 allele frequency of 0.825 (by (NEB # R0175S) enzyme for Csn4F/Dde4R Hardy Weinberg’s Equation) and A1 allele primer product and incubated for 20-25 frequency of 0.067 in pure bred Sahiwal cattle minutes. The restricted products were resolved (Table 1). The amplicons showing A1 allele on 3% gel (Fig.