Furthermore, the newly uncovered compensatory mechanism between DHCR7 and DHCR24 could be of importance for designing medications that would improve cholesterol production in patients with desmosterolosis and Smith-Lemli-Opitz syndrome.
The enzymatic steps impaired in these inborn errors of metabolism include mevolonate kinase (mevalonic aciduria as well as hyperimmunoglobulinemia D and periodic fever syndrome), squalene synthase (Ss-/- mouse), 3beta-hydroxysteroid Delta14-reductase (hydrops-ectopic calcification-moth-eaten skeletal dysplasia), 3beta-hydroxysteroid dehydrogenase (CHILD syndrome, bare patches mouse, and striated mouse), 3beta-hydroxysteroid Delta8,Delta7-isomerase (X-linked dominant chondrodysplasia punctata type 2, CHILD syndrome, and tattered mouse), 3beta-hydroxysteroid Delta24-reductase (desmosterolosis) and 3beta-hydroxysteroid Delta7-reductase (RSH/Smith-Lemli-Opitz syndrome and Dhcr7-/- mouse).
They impair the activity of a putative C3-sterol dehydrogenase (Nshdl, X-linked dominant bare patches/striated mutation in mice), the sterol delta 8-delta 7 isomerase/EBP (Ebp, X-linked dominant tattered mutation in mice; chondrodysplasia punctata (CDPX2) in humans), the delta 24-sterol reductase (autosomal recessive desmosterolosis) and the delta 7-sterol reductase (DHCR7 gene, autosomal recessive Smith-Lemli-Opitz syndrome in humans).
Now known as a Garrodian inborn error caused by the homozygous state of many different autosomal recessive mutations of the 7-dehydrocholesterol reductase gene leading to deficient conversion of 7-dehydrocholesterol to cholesterol, the RSH (so-called Smith-Lemli-Opitz) syndrome has become a paradigmatic metabolic malformation syndrome in a pathway that also involves cause and pathogenesis of desmosterolosis, two forms of the Conradi-Hünermann-Happle type chondodysplasia punctata and its mouse homologs, and the Greenberg "moth-eaten" skeletal dysplasia and the CHILD syndrome.