Leukochimerism genotyping data

Twinning in cattle is infrequent, and also undesired. It can result in
increased occurrence of abortion and dystocia, reduced calf survival, and
a high likelihood of freemartinism in mixed-sex twins. Twin gestations
also commonly are associated with the formation of placental vascular
anastomoses (PVA) between twins. Through this, they share blood, hormones
(leading to freemartinism in mixed-sex twins) and hematopoietic stem
cells, which are the progenitors of white blood cells. The sharing of stem
cells between twins can result in leukochimeric twinsets; these are twins
that have white blood cells derived from both self and co-twin owing to
the fetal migration of hematopoietic stem cells from the extraembryonic
mesoderm of the yolk sac to final sites like bone marrow and thymus. This
study examined the degree to which this leukochimerism changes over time.
DNA was extracted from hair bulbs to determine the individual's true
genotype and blood samples obtained at six time points from 1 week to 8
months of age to assess leukochimerism. Samples were genotyped using a
medium-density SNP chip, and quantitative estimates of allele frequency
were determined using SNPs for which members of a twin set had alternative
homozygous genotypes. Results indicated statistically significant changes
in proportion self and co-twin with age and suggest that by four months of
age, the genotypic mix in white blood cells represents the hematopoietic
cell population resident in the individual.