Dwarfism – Rabbit

The dwarf (dw) mutation in rabbits is responsible for the characteristic small body size seen in dwarf breeds. This trait is primarily associated with a variant in the HMGA2 gene, which plays an important role in growth regulation.

At the molecular level, the mutation consists of a ~12.1 kb deletion affecting the promoter region and the first exons of the HMGA2 gene, resulting in a loss of normal gene function.

The inheritance pattern is autosomal with incomplete dominance:

• Heterozygous rabbits (Dw/dw) display the dwarf phenotype, typically weighing less than 1 kg and showing characteristic features such as a compact body, relatively large head, short snout, and small ears.
• Homozygous mutants (dw/dw), often referred to as “peanuts”, are non-viable and usually die within a few days after birth.
• Wild-type rabbits (Dw/Dw) show normal growth and body size.

In addition to reduced size, dwarf rabbits often show altered craniofacial development, which may predispose them to dental problems.

Although the HMGA2 mutation is a major determinant of dwarfism, studies suggest that additional genes may contribute, indicating a partially polygenic background for body size in rabbits.

From a breeding perspective, mating two dwarf rabbits (heterozygotes) should be avoided, as this results in a proportion of non-viable offspring.