Ovine insulin induced-gene-2: molecular characterization, polymorphisms and association with milk traits Sebastiano Luridiana • Maria Consuelo Mura • Giovanni Cosso • Cinzia Daga • Sara Bodano • Maria Luisa Diaz • Pier Paolo Bini • Vincenzo Carcangiu Received: 26 March 2013 / Accepted: 25 March 2014 / Published online: 3 April 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract The aim was to characterize the INSIG-2 gene in Sarda sheep and to highlight associations between polymorphisms and milk traits. Two-hundred ewes, in their third or fourth lactation who lambed a single lamb between 20th and 30th of November, were chosen. Monthly indi- vidual milk yield was recorded and from each ewe a sample of milk was taken to analyze fat and protein con- tent. PCR–RFLP and DNA sequencing were carried out to detect polymorphisms. Five exons have been characterized and five mutations have been found G88A, 436TCAGdel, A471G, C1071T and T1737G all in the intronic regions. The ovine sequence and related variations were deposited in GenBank with accession number JX843812.1. The ani- mals carrying AA genotype at position 88 showed a lower milk fat concentration than those with the AG or GG genotype (P \ 0.05). A lower milk fat concentration was registered also in the animals with the TCAG deletion in position 436 (P \ 0.05) and in the animals carrying AA genotype at position 471 compared to those with the AG or GG genotype (P \ 0.05). Moreover, the animals carrying CC genotype at position 1071 had a greater milk yield than those with CT or TT genotype (P \ 0.05) while ewes with TT genotype showed a higher milk protein concentration compared to the others (P \ 0.05). A total of 11 haplotypes were detected but no significant associations with milk traits were found. In conclusion for the first time the complete coding sequence of INSIG-2 gene and its asso- ciation with milk trait has been reported in this study. Keywords INSIG-2 gene  Sarda sheep  Polymorphism  Milk traits Introduction Insulin-induced gene (INSIG) is a regulator in lipid metabolism and it consists of two isoforms, -1 and -2, both playing an important role in mediating sterol regulation [1]. The ovine and bovine INSIG-2 gene is located in chro- mosome 2 and is composed of six exons, the first of which is non-coding [2]. INSIGS are two endoplasmic reticulum (ER) members of INSIG proteins family [3] and they appear to mediate reaction of cholesterol synthesis by blocking the activation of sterol regulatory element-bind- ing protein (SREBP) [4]. More in particular they create a sterol-dependent binding to the SREBP cleavage-activating protein (SCAP) and the 3-hydroxy-3-methylglutaryl coen- zyme A reductase (HMG-CoA reductase) proteins [2]. By this way INSIGS cause the ER retention of the SCAP/ SREBP complex and activate the sterol-dependent HMG- CoA reductase degradation [4–7]. Through their binding to INSIG proteins, SCAP and HMG-CoA reductase undertake important tasks in cholesterol homeostasis. SCAP controls the activation of SREBPs which raise the transcription of genes necessary for the synthesis and collection of cho- lesterol [8]. The binding among SCAP and INSIG proteins leads to ER retention of SCAP, thus preventing the release of the SCAP/SREBP complex to the Golgi [4]. This fact explain the reduction in transcriptional rates of SREBP targets and the subsequent reduction in cholesterol synthesis and uptake. The binding between HMG-CoA All the authors contributed equally to the present work. S. Luridiana  M. C. Mura  G. Cosso  C. Daga  S. Bodano  M. L. Diaz  P. P. Bini  V. Carcangiu (&) Dipartimento di Medicina Veterinaria, Universita ` di Sassari, Via Vienna 2, 07100 Sassari, Italy e-mail: endvet@uniss.it 123 Mol Biol Rep (2014) 41:4827–4831 DOI 10.1007/s11033-014-3353-9