Undergraduate honors paper--Mount Holyoke College, 2008. Dept of Biologically Sciences. / Includes bibliographical references (leaves 100-105).

Thesis (Ph. D.)--University of California, San Diego, 1998. / Vita. Includes bibliographical references.

Thesis (D. Med. Scs.)--University of Tartu, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of California, San Diego, and San Diego State University, 2004. / Vita. Includes bibliographical references (leaves 146-163).

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 84-89). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 84-89). Also available on the Internet.

No description available.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Feb. 17, 2009). PDF text: 93 p. : col. ill. ; 4 Mb. UMI publication number: AAT 3328257. Includes bibliographical references. Also available in microfilm and microfiche formats.

Decreased mitochondrial function is associated with aging and is an early step in Alzheimer's disease (AD). Autophagy also declines with age and is required for degradation of dysfunctional mitochondria but it is not known whether autophagosomal formation is overactive and/or degradation of autophagosomes is inhibited in AD. Although two-thirds of the 5 million Americans diagnosed with AD are women, without a clear mechanism. Since the role of gender and autophagy in AD is unclear, we wanted to know whether: A) decreased mitochondrial biogenesis precedes brain plaque formation, neuronal death and memory deficits B) autophagosomal formation is overactive and/or degradation of autophagosomes is inhibited in AD and C) deficits in mitochondrial biogenesis and autophagy occur earlier in life in the hippocampus/cortex of female AD-Tg, than male AD-Tg mice. To answer these questions, mitochondrial DNA (mtDNA), TFAM (transcription factor A mitochondrial) and two stages in autophagy, autophagosomal formation and degradation were measured in the hippocampus/cortex of non-transgenic (non-Tg) and the APP(Swe, DI)/NOS2-/- AD mouse model (AD-Tg) from 2 mo. through 12 mo. of age, when memory deficits develop. Male and female mice were evaluated for gender differences. By measuring mitochondrial gene copy number relative to nuclear gene copy number by qPCR, we found female specific decreases in mtDNA and TFAM protein levels in AD-Tg hippocampus/cortex, before 12 mo., when memory deficits develop. The male AD-Tg mice did not show any decline in the levels of mtDNA or TFAM protein through 12 mo. of age, indicating a decline in mitochondrial biogenesis earlier in life in female AD-Tg mice, than males. To determine whether autophagosomal formation is overactive and/or autophagosomal degradation is inhibited in AD, non-Tg and AD-Tg mouse neurons from 2-12 mo. of age were cultured and transfected with an adenovirus expressing the dual fusion protein, mCherry-GFP-LC3B. This system enables the distinction of early (autophagosomal formation) from late (autophagosomal degradation) stages of autophagy. Autophagosomal formation increased in female AD-Tg mice, while male AD-Tg neurons have decreased formation of autophagosomes, compared to non-Tg. Neurons from AD-Tg mice show deficits in degradation of autophagosomes by 2 mo. Our results show increased autophagosomal formation in female neurons with age and in our AD-like model without corresponding increases in degradation of autophagosomes. All together, our data indicates that the presence of familial APP mutations and knockout of NOS2 increases deficits in both mitochondrial biogenesis and autophagy in female mice, compared to males. These deficits occur before amyloid plaque formation and memory deficits, suggesting that mitochondrial and autophagic deficits may play a role in the higher incidence of AD in females.

Mitochondrial dysfunction causes moderate to profound hearing loss both in isolation and as a feature of multi-systemic mitochondrial disease. The m.1555A > G mitochondrial DNA (mtDNA) variant is associated with a predisposition to aminoglycoside ototoxicity and maternally inherited non-syndromic deafness. However, the reasons for the highly variable penetrance of the associated hearing loss have not yet been fully resolved. Aminoglycosides are a recognised modifier factor of the hearing loss, but cannot account for all hearing impaired carriers in multi-generational pedigrees, implicating additional co-segregating genetic factors. By identifying and characterising the c.3G > A SSBP1 variant as a nuclear modifier of m.1555A > G the work detailed in this thesis extends our understanding of mitochondrial-nuclear interactions in human disease. To ascertain the frequency of the m.1555A > G variant in patients with suspected mitochondrial hearing loss we surveyed the laboratories within the United Kingdom that undertake genetic testing for this variant. We determined that the variant was not found more frequently in patients with known hearing impairment providing further evidence that m.1555A > G does not cause hearing loss in isolation. These results strengthened the case for nuclear genetic modifiers as important contributors to m.1555A > G pathogenesis. We next identified a multi-generational family that transmitted the m.1555A > G variant with variable clinical penetrance of hearing loss. In addition, a cohort of sporadic individuals carrying m.1555A > G was used to test the hypothesis that a conserved genetic mechanism accounted for the phenotype in all carriers. To this effect, we undertook whole exome sequencing in selected familial and sporadic carriers of m.1555A > G, identifying a heterozygous start loss mutation in the core mtDNA replisome protein gene, SSBP1, that co-segregated with the m.1555A > G variant and the phenotype in the family. The SSBP1 variant lead to a perturbation of mtDNA metabolism, and was associated with multiple mtDNA deletions and mtDNA depletion in skeletal muscle. Fibroblasts from these patients also showed mitochondrial network fragmentation and reduced intra-mitochondrial protein synthesis in keeping with the co-existing m.1555A > G variant, leading to reduced proliferation rates under conditions of forced mitochondrial respiration. Our findings provide an explanation for the variable clinical penetrance of the disorder within these m.1555A > G carriers and highlight the importance of trans-acting modifiers in mitochondrial disease.