# Survey of SNPs Associated with Total Number Born and Total Number Born Alive in Pig
## 4 Potential Candidate Genes for Litter Traits of Pig  
Accordingly, Pig QTLdb presents 306 SNPs associated with TNB (218 SNPs) and NBA (88 SNPs) in pigs of various breeds. We should note that 12 SNPs out of 306 SNPs provided in PigQTLdb as a Genome map association with TNB and NBA, are presented twice (add file 1). Perhaps this is due to the fact that the connection of SNPs with TNB and NBA was established in one study, for example, as for SNPs rs81348779 on SSC1 and rs81356698 on SSC2 [23]. These SNPs are localized in the intron of the _UBE3A_ (SSC1) and _EIF3M_ (SSC2) genes. The _UBE3A_ gene encodes _ubiquitin protein ligase E3A_, which plays an essential role in the normal development and functioning of the nervous system, and helps regulate the balance between proteostasis synthesis and degradation in the joints between synapses. Human and mouse _UBE3A_ is maternal imprinted [34]. However, there is no precise information regarding imprinting of pig _UBE3A_. According to the study performed by [PERSON] et al. [35]_UBE3A_ was not imprinted in the skeletal muscle of neonate pigs of Landrace boars and Laiwu sows cross. Further research will probably provide more information to clarify the effects of the _UBE3A_ gene and its and its relation to pig fecundity. The _EIF3M_ gene (the eukaryotic translation initiation factor 3 subunit M) is a complex translation initiation factor consisting of 13 subunits (_EIF3A_-_EIF3M_) and which is involved in mRNA modulation [36]. The _EIF3_ complex is necessary for the key stages of protein synthesis initiation [37]. Previous studies have shown that _EIF3M_ encodes a protein that is critical for mouse embryonic development [38]. In studies performed by [PERSON] et al. [22] a relationship with TNB and NBA was defined for SNPs rs334867206 (intergenic_variant) and rs319494663 (upstream gene variant _ssc-let-7a-2_) on SSC3 and rs81471172 (intron variant _HECWI_) on SSC18. _Sus scrofa let-7a-2 stem-loop (ssc-let-7a-2_) belongs to miRNAs, a class of small non-coding RNAs (-21 nt) that regulate the mRNAs translation on the post-transcriptional level, mainly by binding their targets with the three prime untranslated region (3'-UTR) [39]. A variety of studies have shown that miRNAs can play a potential regulatory role in porcine ovary, testis and spermatogenesis [40; 41; 42]. The _HECWI_ gene, also known as _NEDD4-like ubiquitin protein ligase 1_ (_NEDL1_), is expressed in human neuronal tissues and enhances p53-mediated apoptotic cell death [43]. Supposedly, it regulates the bone morphogenetic protein signaling pathway during embryonic development and bone remodeling [44]. In the work of [PERSON] et al. [25] associations with TNB and NBA are defined for SNP rs342908929, which is localized on SSC6 in the intron of the _ZFYVE9_ gene (_zinc finger FYVE-type containing 9 domain_). The protein encoded by _ZFYVE9_ is involved in the signaling pathway of _transforming growth factor-beta_ (_TGFB_) and directly interacts with _SMAD2_ and _SMAD3_, needed for normal follicular development and ovulation [45]. In the studies performed by [PERSON] et al. [28] a relation with TNB and NBA was defined for SNPs rs80882306 (intergenic variant) on SSC7 and rs319494663 (intron variant PARD3) on SSC10. _PARD3_ (_PAR-3_) is a _scaffold-like PDZ-containing protein_. _PAR-3_ forms a complex with _PAR-6_ and _atypical protein kinase C_ (_PAR-3-atypical protein kinase C-PAR-6 complex_) and is associated with the establishment of cell polarization [46; 47; 48]. [PERSON] [49] argued that mutations in _PARD3_ can also influence the recovery of wounds by weakening the response of the epithelial barrier to a damage or inflammation. Concerning its significant role in the regulation of various stages of ovarian development and the control of steroidogenesis in a ripening follicle [PERSON] et al. [24] studied the _IGFBP-2_ gene (SSC15) and defined SNP rs45435330 associated with TNB and NBA [50]. But more interesting are the variants repeated in two independent studies.