The size of the rabbit from whole genome sequencing: the dwarf-ism in Dwarf Lop breed is better explained as a polygenic trait

The domestication of the European rabbit (Oryctolagus cuniculus) has led to the development of a wide variety of breeds mainly distinguished by a few external traits, such as coat colour and body size. Rabbit breeds are categorized into four major classes based on body size: dwarf, small, medium, and large, with adult body weight ranging from less than 1.0 to more than 3.0 kg. Classical genetic studies and subsequent genomic analyses have shown that body size in rabbit has a polygenic basis, with a major gene determining a type of dwarfism caused by a semi-lethal 12.1 kb deletion in the HMGA2 gene, primarily found in the Netherland Dwarf breed. In this study, our goal was to genetically dissect the dwarfism in another rabbit dwarf breed, the Dwarf Lop. Using a DNA-pool sequencing approach, we obtained whole genome sequencing data from 25 Dwarf Lop rabbits, which was then compared to whole genome se-quencing data obtained using the same approach from six non-dwarf rabbit breeds. Reads were aligned to the rabbit reference genome and single nucleotide with dwarfism in Dwarf Lop rab-bits, pairwise FST analyses were used to compare Dwarf Lop with all other breeds This analysis identified several candidate regions on rabbit chromosomes (OCU) 2, OCU3, OCU7, OCU8, OCU12 OCU14, OCU16, OCU17 and OCU18. These regions contain genes that have already been associated with body size in other species. The most differentiated region was on OCU2, in the position of the LCORL and NCAPG genes, which are well known to affect stature in mammals. The results suggest that the small body size in Dwarf Lop is polygenic with a few major genes. Additionally, the HMGA2 12.1 kb allele is not a major factor influencing the small size in this other dwarf breed. The research was supported by the PSRN (Programma di Sviluppo Rurale Nazionale) Cun-Fu and Cun-Fu 2 projects (co-funded by the European Agricultural Fund for Rural Development of the European Union and by the Italian Ministry of Agriculture, Food Sovereign and Forestry-MASAF) and by the University of Bologna RFO 2024 program.