HLS is associated with HYLS1 mutations. The gene encoding HYLS1 is responsible for proper cilial development within the human body. Cilia are microscopic projections that allow sensory input and signalling output within cells, as well as cell motility.[2] Dysfunction results in a range of abnormalities that are often the result of improper cell signalling.[3] A variant form, HLS2, with additional mutations to the KIF7 gene, is less common.[4]KIF7 also ensures correct cilia formation and function, specifically cilia stability and length.[5]
Hydrolethalus syndrome (HLS) was first mistakenly identified in Finland, during a study on Meckel syndrome.[6] Like HLS, Meckel syndrome presents with severe physiological abnormalities, namely disruptions to the central nervous system and the presence of extra fingers or toes (polydactyly).[6] HLS can be distinguished from Meckel syndrome by analysing kidney function, which is dysfunctional in Meckel syndrome as a result of cyst formation.[7]
^Oka M, Shimojima K, Yamamoto T, Hanaoka Y, Sato S, Yasuhara T, Yoshinaga H, Kobayashi K (June 2016). "A novel HYLS1 homozygous mutation in living siblings with Joubert syndrome". Clinical Genetics. 89 (6): 739–43. doi:10.1111/cge.12752. PMID26830932.
^Putoux A, Thomas S, Coene K, Davis E, Alanay Y, Ogur G, Uz E, Buzas D, Gomes C, Patrier S, Bennett C, Elkhartoufi N, Frison M, Rigonnot L, Joyé N, Pruvost S, Utine G, Boduroglu K, Nitschke P, Fertitta L, Thauvin-Robinet C, Munnich A, Cormier-Daire V, Hennekam R, Colin E, Akarsu N, Bole-Feysot C, Cagnard N, Schmitt A, Goudin N, Lyonnet S, Encha-Razavi F, Siffroi J, Winey M, Katsanis N, Gonzales M, Vekemans M, Beales P, Attié-Bitach T (June 2011). "KIF7 mutations cause fetal hydrolethalus and acrocallosal syndromes". Nature Genetics. 43 (6): 601–6. doi:10.1038/ng.826. PMC3674836. PMID21552264.