BACKGROUND: Formation of the vertebral column is a critical developmental stage in mammals. The strict control of this process has resulted in little variation in number of vertebrae across @entity1 species and no variation within most @entity1 species. The @entity1707 is quite unique as considerable variation exists in number of thoracic vertebrae as well as number of lumbar vertebrae. At least two genes have been identified that affect number of vertebrae in @entity1707 yet considerable genetic variation still exists. Therefore, a genome-wide association (GWA) analysis was conducted to identify additional genomic regions that affect this trait. RESULTS: A total of 1883 animals were phenotyped for the number of ribs and thoracolumbar vertebrae as well as successfully genotyped with the Illumina Porcine SNP60 BeadChip. After data editing, 41,148 SNP markers were included in the GWA analysis. These animals were also phenotyped for @entity1513 . Fifty-three 1  Mb windows each explained at least 1.0  % of the genomic variation for vertebrae counts while 16 regions were significant for @entity1513 . Vertnin genotype significantly affected vertebral counts as well. The region with the largest effect for number of lumbar vertebrae and thoracolumbar vertebrae were located over the Hox B gene cluster and the largest association for thoracic vertebrae number was over the Hox A gene cluster. Genetic markers in significant regions accounted for approximately 50  % of the genomic variation. Less genomic variation for @entity1513 was described by QTL regions and no region was associated with @entity1513 and vertebra counts. CONCLUSIONS: The importance of the Hox gene families in vertebral development was highlighted as significant associations were detected over the A, B and C families. Further evaluation of these regions and characterization of variants within these genes will expand our knowledge on vertebral development using natural genetic variants segregating in commercial @entity1707 .

A study of vertebra number in XXXX confirms the association of vertnin and reveals additional QTL.

@entity1 :: ('9606', 'Species') :: ['mammalian'] @entity1707 :: ('9823', 'Species') :: ['pigs', 'pig', 'swine'] @entity1513 :: ('MESH:D007738', 'Disease') :: ['kyphosis']
@entity1707 :: (9823,Species) :: ['pigs']
