title: Cloning and expression profiling of the VLDLR gene associated with egg performance in duck (Anas platyrhynchos).
abstract: BACKGROUND
  The very low density lipoprotein receptor gene (VLDLR), a member of the low density lipoprotein receptor (LDLR) gene family, plays a crucial role in the synthesis of yolk protein precursors in oviparous species. Differential splicing of this gene has been reported in human, rabbit and rat. In chicken, studies showed that the VLDLR protein on the oocyte surface mediates the uptake of yolk protein precursors into growing oocytes. However, information on the VLDLR gene in duck is still scarce.
  
  
  METHODS
  Full-length duck VLDLR cDNA was obtained by comparative cloning and rapid amplification of cDNA ends (RACE). Tissue expression patterns were analysed by semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR). Association between the different genotypes and egg performance traits was investigated with the general linear model (GLM) procedure of the SAS® software package.
  
  
  RESULTS
  In duck, two VLDLR transcripts were identified, one transcript (variant-a) containing an O-linked sugar domain and the other (variant-b) not containing this sugar domain. These transcripts share ~70 to 90% identity with their counterparts in other species. A phylogenetic tree based on amino acid sequences showed that duck VLDLR proteins were closely related with those of chicken and zebra finch. The two duck VLDLR transcripts are differentially expressed i.e. VLDLR-a is mainly expressed in muscle tissue and VLDLR-b in reproductive organs. We have localized the duck VLDLR gene on chromosome Z. An association analysis using two completely linked SNP sites (T/C at position 2025 bp of the ORF and G/A in intron 13) and records from two generations demonstrated that the duck VLDLR gene was significantly associated with egg production (P < 0.01), age of first egg (P < 0.01) and body weight of first egg (P < 0.05).
  
  
  CONCLUSIONS
  Duck and chicken VLDLR genes probably perform similar function in the development of growing oocytes and deposition of yolk lipoprotein. Therefore, VLDLR could be a candidate gene for duck egg performance and be used as a genetic marker to improve egg performance in ducks.
authors.affiliation: Key Laboratory of Agricultural Animal Genetics, Breeding, and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China.
authors.forename: Cui
authors.initials: C
authors.lastname: Wang
authors.forename: Shi-Jun
authors.initials: SJ
authors.lastname: Li
authors.forename: Wen-Hua
authors.initials: WH
authors.lastname: Yu
authors.forename: Qing-Wu
authors.initials: QW
authors.lastname: Xin
authors.forename: Chuang
authors.initials: C
authors.lastname: Li
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Feng
authors.forename: Xiu-Li
authors.initials: XL
authors.lastname: Peng
authors.forename: Yan-Zhang
authors.initials: YZ
authors.lastname: Gong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004372:Ducks / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D052287:Oviparity; D010058:Oviposition; D010063:Ovum / Q000502:physiology*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D017434:Protein Structure, Tertiary; D040641:Quantitative Trait Loci; D012326:RNA Splicing; D011973:Receptors, LDL / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014714:Vertebrates / Q000145:classification / Q000235:genetics
chemical_list: D011973:Receptors, LDL; C036053:VLDL receptor