title: Elevated Autophagy and Mitochondrial Dysfunction in the Smith-Lemli-Opitz Syndrome.
abstract: Smith-Lemli-Opitz syndrome (SLOS) is a congenital, autosomal recessive metabolic and developmental disorder caused by mutations in the enzyme which catalyzes the reduction of 7-dehydrocholesterol (7DHC) to cholesterol. Herein we show that dermal fibroblasts obtained from SLOS children display increased basal levels of LC3B-II, the hallmark protein signifying increased autophagy. The elevated LC3B-II is accompanied by increased beclin-1 and cellular autophagosome content. We also show that the LC3B-II concentration in SLOS cells is directly proportional to the cellular concentration of 7DHC, suggesting that the increased autophagy is caused by 7DHC accumulation secondary to defective DHCR7. Further, the increased basal LC3B-II levels were decreased significantly by pretreating the cells with antioxidants implicating a role for oxidative stress in elevating autophagy in SLOS cells. Considering the possible source of oxidative stress, we examined mitochondrial function in the SLOS cells using JC-1 assay and found significant mitochondrial dysfunction compared to mitochondria in control cells. In addition, the levels of PINK1 which targets dysfunctional mitochondria for removal by the autophagic pathway are elevated in SLOS cells, consistent with mitochondrial dysfunction as a stimulant of mitophagy in SLOS. This suggests the increase in autophagic activity may be protective, i.e., to remove dysfunctional mitochondria. Taken together, these studies are consistent with a role for mitochondrial dysfunction leading to increased autophagy in SLOS pathophysiology.
authors.affiliation: Department of Surgery, Cooper University Hospital, Cooper Medical School at Rowan University, Camden, NJ 08103.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Chang
authors.affiliation: Department of Surgery, Cooper University Hospital, Cooper Medical School at Rowan University, Camden, NJ 08103.
authors.forename: Gongyi
authors.initials: G
authors.lastname: Ren
authors.affiliation: Department of Surgery, Cooper University Hospital, Cooper Medical School at Rowan University, Camden, NJ 08103.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Steiner
authors.affiliation: Departments of Pediatrics and Molecular & Medical Genetics, Institute for Development and Disability, Doernbecher Children's Hospital, Oregon Health & Science University, Portland, OR.
authors.forename: Louise
authors.initials: L
authors.lastname: Merkens
authors.affiliation: Departments of Pediatrics and Molecular & Medical Genetics, Institute for Development and Disability, Doernbecher Children's Hospital, Oregon Health & Science University, Portland, OR.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Roullet
authors.affiliation: Department of Psychiatry, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University Nashville, Tennessee.
authors.forename: Zeljka
authors.initials: Z
authors.lastname: Korade
authors.affiliation: Department of Surgery, Thomas Jefferson University College of Medicine, Philadelphia, PA19107.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: DiMuzio
authors.affiliation: Department of Surgery, Cooper University Hospital, Cooper Medical School at Rowan University, Camden, NJ 08103.
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Tulenko
keywords: 7-dehydrocholesterol; birth defects; lysosomes; mitophagy; β-hydroxy-steroid-Δ7-reductase (DHCR7)