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Open Access Publications from the University of California

Scholarly Works (7 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2018)

Retinal degeneration are blinding eye diseases that impact millions of lives around the world. Age-related macular degeneration alone is predicted to affect over 250 million people around 2040 as the population ages. The most prevalent form of inherited retinal degeneration, retinitis pigmentosa, has been found to have more than 200 different causative mutations, showing that treatments for retinal degeneration may not have a one-size-fit-all solution and require different approaches and concerted efforts from scientists around the world.

Gene therapy is an emerging and effective treatment option in restoring the vision and the quality of life of a subset of retinal degenerative patients. However, the success of gene therapy faces the limitations of low vector transduction efficiency, low vector carrying capacity, and immutable disease progression. Stem cell therapies face similar problems of immunogenicity and low cell integration efficiency. We show here that, through a combination of these two treatment modalities, endogenous regeneration through the genetic reprogramming of glia may be another effective and more broadly applicable approach in treating retinal degeneration.

Müller cells, the primary glia of the retina, have been demonstrated to possess neuroprotective as well as retinal progenitor cell-like regenerative properties in cases of retinal damage in zebrafish. The helix-loop-helix transcription factor Ascl1 is a key factor in determining neuronal cell fate in the nervous system, and it has also been shown to be capable of transdifferentiating astrocytes as well as Müller glia into neurons in vitro. The Let7 siRNA regulator Lin28 likewise seems to influence the zebrafish Müller glia cell fate through an Ascl1-dependent manner. While damage-dependent regeneration of the retina in zebrafish relies on the expression of Ascl1 and Lin28, no large scale proliferation and differentiation of the Müller glia have been observed in the mammalian retina, and as such, the role of Ascl1 and Lin28 in determining the mammalian Müller glia cell fate is currently unknown.

In chapter 2, we demonstrate that Müller glia in zebrafish and mice are capable of proliferation and fate change in vivo through the approach of forced expression of both Ascl1 and Lin28. Lin28 enhances the Ascl1-dependent proliferation of the Müller glia in zebrafish and mice when retinal damage is induced via NMDA. Notch suppression increases this proliferation in zebrafish further, but curiously not in mice. In chapter 3 we look at the different conditions involved in this Ascl1/Lin28 dependent proliferation through the exploration of different retinal damage models such as cobalt chloride induced hypoxic response and UV light induced photoreceptor apoptosis. We also attempt to induce Müller glia proliferation in retinal degenerative mouse models. Interestingly, while we find some success in inducing Müller glia proliferation in the retinal damage models, we find that genetic mouse models of retinal degeneration do not seem to respond to Ascl1 and Lin28 manipulation.

    Cover page: Endogenous Induced Cell Fate Change of the Müller Glia in Different Models of Retinal Degeneration
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2018)
    Müller glial (MG) cells in the zebrafish retina respond to injury by acquiring retinal stem-cell characteristics. Thousands of gene expression changes are associated with this event. Key among these changes is the induction of Ascl1a and Lin28a, two reprogramming factors whose expression is necessary for retina regeneration. Whether these factors are sufficient to drive MG proliferation and subsequent neuronal-fate specification remains unknown. To test this, we conditionally expressed Ascl1a and Lin28a in the uninjured retina of male and female fish. We found that together, their forced expression only stimulates sparse MG proliferation. However, in combination with Notch signaling inhibition, widespread MG proliferation and neuron regeneration ensued. Remarkably, Ascl1 and Lin28a expression in the retina of male and female mice also stimulated sparse MG proliferation, although this was not enhanced when combined with inhibitors of Notch signaling. Lineage tracing in both fish and mice suggested that the proliferating MG generated multipotent progenitors; however, this process was much more efficient in fish than mice. Overall, our studies suggest that the overexpression of Ascl1a and Lin28a in zebrafish, in combination with inhibition of Notch signaling, can phenocopy the effects of retinal injury in Müller glia. Interestingly, Ascl1 and Lin28a seem to have similar effects in fish and mice, whereas Notch signaling may differ. Understanding the different consequences of Notch signaling inhibition in fish and mice, may suggest additional strategies for enhancing retina regeneration in mammals.SIGNIFICANCE STATEMENT Mechanisms underlying retina regeneration in fish may suggest strategies for stimulating this process in mammals. Here we report that forced expression of Ascl1 and Lin28a can stimulate sparse MG proliferation in fish and mice; however, only in fish does Notch signaling inhibition collaborate with Ascl1a and Lin28a to stimulate widespread MG proliferation in the uninjured retina. Discerning differences in Notch signaling between fish and mice MG may reveal strategies for stimulating retina regeneration in mammals.
      Cover page: Notch Suppression Collaborates with Ascl1 and Lin28 to Unleash a Regenerative Response in Fish Retina, But Not in Mice
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2022)

      Objective

      Individuals with schizophrenia carry a high burden of cardiovascular disease and elevated rates of sudden cardiac arrest (SCA), but little published data is available regarding survival from SCA in this population. The authors compared cardiovascular disease burden and resuscitation outcomes following SCA in individuals with and without schizophrenia.

      Methods

      Case-control analysis drawn from a prospective community-based study of SCA in a large community. The authors defined cases as having a pre-SCA history of schizophrenia, and controls as individuals with SCA without a history of schizophrenia. SCA cases with schizophrenia were compared to a 1:5 age- and sex-frequency-matched sample of SCA cases without schizophrenia.

      Results

      The 103 SCA schizophrenia cases were as likely as the 515 cases without schizophrenia to have resuscitation attempted (75% vs. 80%; p = 0.24) and had a shorter 911 call mean response time (5.8 min vs. 6.9 min, p < 0.001). However, they were significantly less likely to present with a shockable rhythm (ventricular fibrillation/pulseless ventricular tachycardia 16% vs. 43%, p < 0.001), and less likely to survive to hospital discharge (3% vs. 14%, p = 0.008). Pre-arrest cardiovascular disease burden was similar in patients with and without schizophrenia.

      Conclusions

      Despite comparable resuscitation characteristics and cardiovascular disease burden, patients with schizophrenia had significantly lower rates of SCA survival. The paucity of previous research into this phenomenon warrants further investigation to identify factors that may improve survival.
        Cover page: Sudden cardiac arrest in patients with schizophrenia: A population-based study of resuscitation outcomes and pre-existing cardiovascular disease
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2015)
        Mutations in the cellular retinaldehyde-binding protein (CRALBP, encoded by RLBP1) can lead to severe cone photoreceptor-mediated vision loss in patients. It is not known how CRALBP supports cone function or how altered CRALBP leads to cone dysfunction. Here, we determined that deletion of Rlbp1 in mice impairs the retinal visual cycle. Mice lacking CRALBP exhibited M-opsin mislocalization, M-cone loss, and impaired cone-driven visual behavior and light responses. Additionally, M-cone dark adaptation was largely suppressed in CRALBP-deficient animals. While rearing CRALBP-deficient mice in the dark prevented the deterioration of cone function, it did not rescue cone dark adaptation. Adeno-associated virus-mediated restoration of CRALBP expression specifically in Müller cells, but not retinal pigment epithelial (RPE) cells, rescued the retinal visual cycle and M-cone sensitivity in knockout mice. Our results identify Müller cell CRALBP as a key component of the retinal visual cycle and demonstrate that this pathway is important for maintaining normal cone-driven vision and accelerating cone dark adaptation.
          Cover page: CRALBP supports the mammalian retinal visual cycle and cone vision
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2014)

          Background

          In cohort studies, elevated levels of plasma nonesterified free fatty acids (NEFAs) have been associated with increased risk of sudden cardiac death (SCD) in men, but blood samples were drawn several years before SCD.

          Objective

          To confirm this relationship by evaluating levels of plasma NEFAs at the time of the SCD event in a group of both men and women.

          Methods

          From the ongoing Oregon Sudden Unexpected Death Study, we compared levels of plasma NEFAs in 149 SCD cases presenting with ventricular fibrillation (mean age 64 ± 12 years; 73% men) and 149 age- and sex-matched controls with coronary artery disease. Plasma was processed from blood drawn at the time of arrest (cases) and at a routine visit (controls). The levels of plasma NEFAs were compared after categorizing into quartiles on the basis of control values. Conditional logistic regression was used to predict adjusted odds ratio for SCD associated with plasma NEFA levels per increased quartile.

          Results

          The plasma NEFA levels were significantly higher in SCD cases than in controls (median 0.39 mmol/L [interquartile range 0.28-0.60 mmol/L] vs 0.32 mmol/L [interquartile range 0.20-0.49 mmol/L]; P = .002). There were no significant differences in body mass index, smoking, and diabetes. The odds ratio for SCD was 1.42 (95% confidence interval 1.14-1.78) per quartile increase in the plasma NEFA level (P = .002). Individuals with plasma NEFA levels above the prespecified cutoff point of 0.32 mmol/L were at increased risk of SCD (odds ratio 2.00; 95% confidence interval 1.20-3.34; P = .008).

          Conclusion

          These findings strengthen the role of plasma NEFA as a potential biomarker for the assessment of SCD risk.
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2015)

            Background

            Genome-wide association studies and candidate-gene based approaches have identified multiple common variants associated with increased risk of sudden cardiac death (SCD). However, the independent contribution of these individual loci to disease risk is modest.

            Objective

            To investigate the cumulative effects of genetic variants previously associated with SCD risk.

            Methods

            A total of 966 SCD cases from the Oregon-Sudden Unexpected Death Study and 1,926 coronary artery disease controls from the Wellcome Trust Case-Control Consortium were investigated. We generated genetic risk scores (GRS) for each trait composed of variants previously associated with SCD or with abnormalities in specific electrocardiographic traits such as QRS duration, QTc interval and heart rate. GRSs were calculated using a weighted approach based on the number of risk alleles weighted by the beta coefficients derived from the original studies. We also compared the highest and lowest quintiles for the GRS composed of SCD SNPs.

            Results

            Increased cumulative risk was observed for a GRS composed of 14 SCD-SNPs (OR=1.17 [1.05-1.29], P = 0.002). The risk for SCD was 1.5 fold higher in the highest quintile when compared to the lowest quintile (OR = 1.46[1.11-1.92]). We did not observe significant associations with SCD for SNPs that determine electrocardiographic traits.

            Conclusions

            A modest but significant effect on SCD risk was identified for a GRS composed of 14 previously associated SCD SNPs. While next generation sequencing methodology will continue to identify additional novel variants, these findings represent proof of concept for the additive effects of gene variants on SCD risk.
              Cover page: Cumulative effects of common genetic variants on risk of sudden cardiac death
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2013)

              Background

              Recent genome-wide association studies (GWAS) have identified novel loci associated with sudden cardiac death (SCD). Despite this progress, identified DNA variants account for a relatively small portion of overall SCD risk, suggesting that additional loci contributing to SCD susceptibility await discovery. The objective of this study was to identify novel DNA variation associated with SCD in the context of coronary artery disease (CAD).

              Methods and findings

              Using the MetaboChip custom array we conducted a case-control association analysis of 119,117 SNPs in 948 SCD cases (with underlying CAD) from the Oregon Sudden Unexpected Death Study (Oregon-SUDS) and 3,050 controls with CAD from the Wellcome Trust Case-Control Consortium (WTCCC). Two newly identified loci were significantly associated with increased risk of SCD after correction for multiple comparisons at: rs6730157 in the RAB3GAP1 gene on chromosome 2 (P = 4.93×10(-12), OR = 1.60) and rs2077316 in the ZNF365 gene on chromosome 10 (P = 3.64×10(-8), OR = 2.41).

              Conclusions

              Our findings suggest that RAB3GAP1 and ZNF365 are relevant candidate genes for SCD and will contribute to the mechanistic understanding of SCD susceptibility.
                Cover page: Novel Loci Associated with Increased Risk of Sudden Cardiac Death in the Context of Coronary Artery Disease
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