Browsing by Author "Weiss, Michael"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Generation and mutational analysis of a transgenic mouse model of human SRY
    (Wiley, 2022-03) Thomson, Ella; Zhao, Liang; Chen, Yen-Shan; Longmuss, Enya; Ng, Ee Ting; Sreenivasan, Rajini; Croft, Brittany; Song, Xin; Sinclair, Andrew; Weiss, Michael; Pelosi, Emanuele; Koopman, Peter; Biochemistry and Molecular Biology, School of Medicine
    SRY is the Y-chromosomal gene that determines male sex development in humans and most other mammals. After three decades of study, we still lack a detailed understanding of which domains of the SRY protein are required to engage the pathway of gene activity leading to testis development. Some insight has been gained from the study of genetic variations underlying differences/disorders of sex determination (DSD), but the lack of a system of experimentally generating SRY mutations and studying their consequences in vivo has limited progress in the field. To address this issue, we generated a mouse model carrying a human SRY transgene able to drive testis determination in XX mice. Using CRISPR-Cas9 gene editing, we generated novel genetic modifications in each of SRY's three domains (N-terminal, HMG box, and C-terminal) and performed a detailed analysis of their molecular and cellular effects on embryonic testis development. Our results provide new functional insights unique to human SRY and present a versatile and powerful system in which to functionally analyze variations of SRY including known and novel pathogenic variants found in DSD.
  • Thumbnail Image
    Item
    OR15-5 Human Sex Determination at the Edge of Ambiguity: Impaired SRY Phosphorylation Attenuates Expression of the Male Program
    (Oxford University Press, 2019-04-15) Chen, Yen-Shan; Racca, Joseph; Phillips, Nelson; Weiss, Michael; Medicine, School of Medicine
    A paradox is posed by metazoan gene-regulatory networks (GRNs) that are robust yet evolvable. Insight may be obtained through studies of bistable genetic circuits mediating developmental decisions. A model in organogenesis is provided by the sex-specific differentiation of the embryonic gonadal ridge to form a testis or ovary. Here, we investigated a Swyer mutation in human testis-determining factor SRY that impairs its phosphorylation in association with variable developmental outcomes: fertile male, intersex, or infertile female (46, XY pure gonadal dysgenesis). The mutation (R30I) abrogates serine phosphorylation within a putative target site for protein kinase A (PKA) N-terminal to the HMG box. Diverse processes can be regulated by protein phosphorylation, including DNA recognition by transcription factors (TFs). Phosphorylation of this site in human SRY (LRRSSSFLCT; italics) in vitro was previously shown to enhance specific DNA affinity. Biological consequences of the mutation were evaluated in SRY-responsive mammalian cell lines following transient transfection. The mutation attenuated in concert occupancy of a target enhancer (TESCO) and SOX9 transcriptional activation. These perturbations were mitigated by acidic substitution (LRIDDDFL) whereas Ala substitutions (RRAAAFL or RIAAAFL) attenuated activity to an extent similar to R30I alone. No differences were observed in nuclear localization. Mutagenesis suggested that the central Ser is most efficiently phosphorylated in accord with PKA targeting rules. Replacement of the native site by an optimized “Kemptide” PKA site (LRRASLGCT) enhanced both SRY phosphorylation and SOX9 transcriptional activation whereas a “swapped” protein-kinase C determinant (LRRSSFRRCT) blocked phosphorylation. Among SRY variants, extent of cellular phosphorylation mirrored relative in vitro efficiencies of synthetic SRY-derived peptides as PKA-specific substrates. Although several kinases are predicted in silico to target this tri-serine motif, cell-based studies implicate PKA as the relevant kinase in vivo. Our results provide evidence that primate Sry requires its phosphorylation for full gene-regulatory activity. A PKA site N-terminal to the SRY HMG box, unique to primates, exemplifies network “tinkering” through recruitment of a new regulatory linkage. Molecular characterization of the R30I inherited Swyer mutation in SRY thus demonstrates that impaired TF phosphorylation can attenuate a human developmental switch at the edge of ambiguity.
  • Thumbnail Image
    Item
    A Phase 2, Double-Blind, Randomized, Dose-Ranging Trial Of Reldesemtiv In Patients With ALS
    (Taylor & Francis, 2021-05) Shefner, Jeremy M.; Andrews, Jinsy A.; Genge, Angela; Jackson, Carlayne; Lechtzin, Noah; Miller, Timothy M.; Cockroft, Bettina M.; Meng, Lisa; Wei, Jenny; Wolff, Andrew A.; Malik, Fady I.; Bodkin, Cynthia; Brooks, Benjamin R.; Caress, James; Dionne, Annie; Fee, Dominic; Goutman, Stephen A.; Goyal, Namita A.; Hardiman, Orla; Hayat, Ghazala; Heiman-Patterson, Terry; Heitzman, Daragh; Henderson, Robert D.; Johnston, Wendy; Karam, Chafic; Kiernan, Matthew C.; Kolb, Stephen J.; Korngut, Lawrence; Ladha, Shafeeq; Matte, Genevieve; Mora, Jesus S.; Needham, Merrilee; Oskarsson, Bjorn; Pattee, Gary L.; Pioro, Erik P.; Pulley, Michael; Quan, Dianna; Rezania, Kourosh; Schellenberg, Kerri L.; Schultz, David; Shoesmith, Christen; Simmons, Zachary; Statland, Jeffrey; Sultan, Shumaila; Swenson, Andrea; Van Den Berg, Leonard H.; Vu, Tuan; Vucic, Steve; Weiss, Michael; Whyte-Rayson, Ashley; Wymer, James; Zinman, Lorne; Rudnicki, Stacy A.; Neurology, School of Medicine
    To evaluate safety, dose response, and preliminary efficacy of reldesemtiv over 12 weeks in patients with amyotrophic lateral sclerosis (ALS). Methods: Patients (≤2 years since diagnosis) with slow upright vital capacity (SVC) of ≥60% were randomized 1:1:1:1 to reldesemtiv 150, 300, or 450 mg twice daily (bid) or placebo; active treatment was 12 weeks with 4-week follow-up. Primary endpoint was change in percent predicted SVC at 12 weeks; secondary measures included ALS Functional Rating Scale-Revised (ALSFRS-R) and muscle strength mega-score. Results: Patients (N = 458) were enrolled; 85% completed 12-week treatment. The primary analysis failed to reach statistical significance (p = 0.11); secondary endpoints showed no statistically significant effects (ALSFRS-R, p = 0.09; muscle strength mega-score, p = 0.31). Post hoc analyses pooling all active reldesemtiv-treated patients compared against placebo showed trends toward benefit in all endpoints (progression rate for SVC, ALSFRS-R, and muscle strength mega-score (nominal p values of 0.10, 0.01 and 0.20 respectively)). Reldesemtiv was well tolerated, with nausea and fatigue being the most common side effects. A dose-dependent decrease in estimated glomerular filtration rate was noted, and transaminase elevations were seen in approximately 5% of patients. Both hepatic and renal abnormalities trended toward resolution after study drug discontinuation. Conclusions: Although the primary efficacy analysis did not demonstrate statistical significance, there were trends favoring reldesemtiv for all three endpoints, with effect sizes generally regarded as clinically important. Tolerability was good; modest hepatic and renal abnormalities were reversible. The impact of reldesemtiv on patients with ALS should be assessed in a pivotal Phase 3 trial. (ClinicalTrials.gov Identifier: NCT03160898).
  • Thumbnail Image
    Item
    Towards Better Diabetes Therapeutics: Designing a More Stable Insulin Analog
    (2023-03) Sambou Oumarou, Oumoul Ghaniyya Faiza; Weiss, Michael; Georgiadis, Millie M.; Hoang, Quyen Q.; Sims, Emily
    Insulin is a hormone that plays a central role in the regulation of human metabolism, and as a drug, is used in the treatment of diabetes mellitus. Hyperglycemia characterizes this condition due to a range of reasons from impaired insulin production by pancreatic beta cells to abnormalities resulting in resistance to insulin action. Depending on time and mechanism of action, the main types of insulin analogs are basal and prandial. Basal insulin analogs are slow-acting insulins that maintain a continuous basal level of insulin in the bloodstream. Prandial insulin analogs are fast-acting and their therapeutic goal is to avoid immediate and late post-prandial hyperglycemia. Most analogs face the problem of chemical degradation and amyloid-like fibril formation (fibrillation) in delivery devices. Thus, many modifications have been made to insulin in the effort to make it more stable and faster-acting. This thesis aims to study the effects of modifications that could be used to design an insulin analog with improved chemical and physical properties, while maintaining biological activity. We studied six amino-acid substitutions to native human insulin in different combinations: desB1 , AB2 , EB3, EA8 , EA14, and EB29. Analogs of the protein were chemically synthesized. Then, fibrillation and circular dichroism assays were performed using purified proteins. The results suggested that EB3 and EA14 are stabilizing modifications that prevent fibril formation, whereas EA8 and EA14 increase the structural stability of an analog. Our findings also suggested that certain modifications in isolation may not impact overall stability, but when combined with others, may show detectable effects, which is why EA8 and EA14 became the focus of further experiments. Cell-based activity assays indicated that all the analogs had similar biological activities. Future work will assess chemical degradation, solubility, amide proton exchange (as monitored by NMR), and mitogenicity.