Smith Lemli Opitz syndrome (SLOS) is an inherited malformation and mental retardation metabolic disorder with no cure. Mutations in the last enzyme of the cholesterol biosynthetic pathway, 7-dehydrocholesterol reductase (DHCR7), lead to cholesterol insufficiency and accumulation of its dehyrdocholesterol precursors, and contribute to its pathogenesis. The central nervous system (CNS) constitutes a major pathophysiological component of this disorder and remains unamenable to dietary cholesterol therapy due to the impenetrability of the blood brain barrier (BBB). The goal of this study was to restore sterol homeostasis in the CNS. To bypass the BBB, gene therapy using an adeno-associated virus (AAV-8) vector carrying a functional copy of the DHCR7 gene was administered by intrathecal (IT) injection directly into the cerebrospinal fluid of newborn mice. Two months post-treatment, vector DNA and DHCR7 expression was observed in the brain and a corresponding improvement of sterol levels seen in the brain and spinal cord. Interestingly, sterol levels in the peripheral nervous system also showed a similar improvement. This study shows that IT gene therapy can have a positive biochemical effect on sterol homeostasis in the central and peripheral nervous systems in a SLOS animal model. A single dose delivered three days after birth had a sustained effect into adulthood, eight weeks post-treatment. These observations pave the way for further studies to understand the effect of biochemical improvement of sterol levels on neuronal function, to provide a greater understanding of neuronal cholesterol homeostasis, and to develop potential therapies.

Both enzyme activity and mRNA concentration of beta-glucuronidase were measured in kidneys of mice treated with testosterone and the synthetic estrogen, diethylstilbestrol. Six congenic strains, all having a C57BL6/J genetic background but each having a different haplotype of the beta-glucuronidase gene complex, were compared. In each strain the induction caused by androgen was partially repressed by estrogen. The extent of this antagonism varied among the six haplotypes and was not coordinate with the extent of induction by androgen alone. Antagonism appears to be regulated by at least two alleles of a new locus, Gus-e, within the beta-glucuronidase gene complex. Repression by estrogen, like induction by androgen, appears to take place primarily at the transcriptional level. Kinetic studies revealed that estrogen causes the androgen response curve to plateau earlier and at a lower level. This suggests that estrogen increases the rate of gene deactivation rather than decreasing the rate of gene activation. Isoelectric focusing of beta-glucuronidase from Gus-ea and Gus-eb mice and their F1 progeny revealed that the genes are regulated in cis. Together, these findings support a model in which both sex hormones exert their effects on separate DNA response elements located in close proximity to the gene or within the gene itself.

No abstract

No abstract