Biology of KAL1 and its orthologs: Implications for X-linked Kallmann syndrome and the search for novel candidate genes

Kallmann syndrome is characterised by congenital hypogonadotropic hypogonadism and anosmia, sometimes with other non-reproductive defects. Although multiple genetic pathways are now known to be involved in the development of this disorder, KAL1, the gene causing the X-linked form of Kallmann syndrome was the first to be identified. It has thus been extensively studied both in vitro and in vivo, though the absence of an identifiable murine ortholog has denied researchers the opportunity to create and study Kal-1 knock-out mice. This review looks at several studies in species with a kal-1 ortholog, revealing functional similarities with the human disorder. Further work has shown that the kal-1 domain structure is maintained across genera, that it controls similar morphological and cellular processes during development, and that data from the nematode Caenorhabditis elegans, in particular, may point to novel human candidate genes.