Skin lesions,
cataracts, and congenital anomalies have been frequently associated with inherited deficiencies in
enzymes that synthesize
cholesterol.
Lanosterol synthase (LSS) converts (S)-2,3-epoxysqualene to
lanosterol in the
cholesterol biosynthesis pathway. Biallelic mutations in LSS have been reported in families with congenital
cataracts and, very recently, have been reported in cases of
hypotrichosis. However, it remains to be clarified whether these phenotypes are caused by LSS enzymatic deficiencies in each tissue, and disruption of LSS enzymatic activity in vivo has not yet been validated. We identified two patients with novel biallelic LSS mutations who exhibited congenital
hypotrichosis and midline anomalies but did not have
cataracts. We showed that the blockade of the LSS
enzyme reaction occurred in the patients by measuring the (S)-2,3-epoxysqualene/
lanosterol ratio in the forehead sebum, which would be a good
biomarker for the diagnosis of LSS deficiency. Epidermis-specific Lss knockout mice showed neonatal lethality due to
dehydration, indicating that LSS could be involved in skin barrier integrity.
Tamoxifen-induced knockout of Lss in the epidermis caused
hypotrichosis in adult mice. Lens-specific Lss knockout mice had
cataracts. These results confirmed that LSS deficiency causes
hypotrichosis and
cataracts due to loss-of-function mutations in LSS in each tissue. These mouse models will lead to the elucidation of the pathophysiological mechanisms associated with disrupted LSS and to the development of therapeutic treatments for LSS deficiency.