Effects on neonatal growth of the Hba(th-j) deletion on mouse chromosome 11 are not due to genomic imprinting.

The Hba(th-j) deletion is found proximally on mouse chromosome 11 in a region of the genome that contains imprinted sequences important for neonatal growth regulation. This study has examined the effect of genomic imprinting on neonatal growth of offspring heterozygous for the Hba(th-j) deletion. Transmission of the deletion through both the male and female germ lines has shown that offspring heterozygous for the deletion are growth retarded when compared to wild type litter mates. This growth retardation is associated with the heterozygous genotype regardless from which parent the deletion is inherited. Growth of both wild type and Hba(th-j)/+ neonates born from Hba(th-j)/+ mothers is compromised when compared to offspring from wild type mothers indicating a maternal effect of the deletion on neonatal growth. These data demonstrate that sequences present in the Hba(th-j) deletion are important for growth regulation but that the expression of these sequences is not regulated by genomic imprinting.