GM3 Synthase Deficiency (GM3SD) is a neurodevelopmental disorder resulting from pathogenic variants in the ST3GAL5 gene, which encodes GM3 synthase, a glycosphingolipid (GSL)-specific sialyltransferase. This enzyme adds a sialic acid to the terminal galactose of lactosylceramide (LacCer) to produce the monosialylated ganglioside GM3. In turn, GM3 is extended by other glycosyltransferases to generate nearly all the complex gangliosides enriched in neural tissue. Pathogenic mechanisms underlying the neural phenotypes associated with GM3SD are unknown. To explore how loss of GM3 impacts neural-specific glycolipid glycosylation and cell signaling, GM3SD patient fibroblasts bearing one of two different ST3GAL5 variants were reprogrammed to induced pluripotent stem cells (iPSCs) and then differentiated to neural crest cells (NCCs). GM3 and GM3-derived gangliosides were undetectable in cells carrying either variant, while LacCer precursor levels were elevated compared to wildtype (WT). NCCs of both variants synthesized elevated levels of neutral lacto- and globo-series, as well as minor alternatively sialylated GSLs compared to WT. Ceramide profiles were also shifted in GM3SD variant cells. Altered GSL profiles in GM3SD cells were accompanied by dynamic changes in the cell surface proteome, protein O-GlcNAcylation, and receptor tyrosine kinase abundance. GM3SD cells also exhibited increased apoptosis and sensitivity to erlotinib-induced inhibition of epidermal growth factor receptor signaling. Pharmacologic inhibition of O-GlcNAcase rescued baseline and erlotinib-induced apoptosis. Collectively, these findings indicate aberrant cell signaling during differentiation of GM3SD iPSCs and also underscore the challenge of distinguishing between variant effect and genetic background effect on specific phenotypic consequences.
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The primary goal of our research will always be to find effective and affordable treatments for patients. Over the years, we have shared our methods and discoveries with the broader scientific community.
In the over 30 years since the Clinic's founding, our staff have published more than 120 peer-reviewed research papers, fueled by close collaboration between our clinical and laboratory teams and effective relationships with academic, scientific, and clinical partners.
Authors: Kevin A. Strauss, Vincent J. Carson, Emilienne Bolettieri, Mariah Everett, Ashton Bollinger, Lauren E. Bowser, Keturah Beiler, Millie Young, Simon Edvardson, Nitay Fraenkel, Adele D'Amico, Enrico Bertini, Lokesh Lingappa, Devyani Chowdhury, Linda P. Lowes, Megan Iammarino, Lindsay N. Alfano, Karlla W. Brigatti
We created WiTNNess as a hybrid prospective/cross-sectional observational study to simulate a clinical trial for infantile-onset TNNT1 myopathy. Our aims were to identify populations for future trial enrollment, rehearse outcome assessments, specify endpoints, and refine trial logistics.
Authors: Huiya Yang, Robert H Brown Jr, Dan Wang, Kevin A Strauss, Guangping Gao
GM3 synthase deficiency (GM3SD) is an infantile-onset epileptic encephalopathy syndrome caused by biallelic loss-of-function mutations in ST3GAL5. Loss of ST3GAL5 activity in humans results in systemic ganglioside deficiency and severe neurological impairment. No disease-modifying treatment is currently available. Certain recombinant adeno-associated viruses (rAAVs) can cross the blood-brain barrier to induce widespread, long-term gene expression in the CNS and represent a promising therapeutic strategy. Here, we show that a first-generation rAAV-ST3GAL5 replacement vector using a ubiquitous promoter restored tissue ST3GAL5 expression and normalized cerebral gangliosides in patient-derived induced pluripotent stem cell neurons and brain tissue from St3gal5-KO mice but caused fatal hepatotoxicity when administered systemically. In contrast, a second-generation vector optimized for CNS-restricted ST3GAL5 expression, administered by either the intracerebroventricular or i.v. route at P1, allowed for safe and effective rescue of lethality and behavior impairment in symptomatic GM3SD mice up to a year. These results support further clinical development of ST3GAL5 gene therapy.
Authors: Laura J Grange, John J Reynolds, Farid Ullah, Bertrand Isidor, Robert F Shearer, Xenia Latypova, Ryan M Baxley, Antony W Oliver, Anil Ganesh, Sophie L Cooke, Satpal S Jhujh, Gavin S McNee, Robert Hollingworth, Martin R Higgs, Toyoaki Natsume, Tahir Khan, Gabriel A Martos-Moreno, Sharon Chupp, Christopher G Mathew, David Parry, Michael A Simpson, Nahid Nahavandi, Zafer Yuksel, Mojgan Drasdo, Anja Kron, Petra Vogt, Annemarie Jonasson, Saad Ahmed Seth, Claudia Gonzaga-Jauregui, Karlla W Brigatti, Alexander P A Stegmann, Masato Kanemaki, Dragana Josifova, Yuri Uchiyama, Yukiko Oh, Akira Morimoto, Hitoshi Osaka, Zineb Ammous, Jesus Argente, Naomichi Matsumoto, Constance T R M Stumpel, Alexander M R Taylor, Andrew P Jackson, Anja-Katrin Bielinksy, Niels Mailand, Cedric Le Caignec, Erica E Davis, Grant S Stewart
Embryonic development is dictated by tight regulation of DNA replication, cell division and differentiation. Mutations in DNA repair and replication genes disrupt this equilibrium, giving rise to neurodevelopmental disease characterized by microcephaly, short stature and chromosomal breakage. Here, we identify biallelic variants in two components of the RAD18-SLF1/2-SMC5/6 genome stability pathway, SLF2 and SMC5, in 11 patients with microcephaly, short stature, cardiac abnormalities and anemia. Patient-derived cells exhibit a unique chromosomal instability phenotype consisting of segmented and dicentric chromosomes with mosaic variegated hyperploidy. To signify the importance of these segmented chromosomes, we have named this disorder Atelís (meaning – incomplete) Syndrome. Analysis of Atelís Syndrome cells reveals elevated levels of replication stress, partly due to a reduced ability to replicate through G-quadruplex DNA structures, and also loss of sister chromatid cohesion. Together, these data strengthen the functional link between SLF2 and the SMC5/6 complex, highlighting a distinct role for this pathway in maintaining genome stability.
Authors: Kevin A. Strauss, Michelle A. Farrar, Francesco Muntoni, Kayoko Saito, Jerry R. Mendell, Laurent Servais, Hugh J. McMillan, Richard S. Finkel, Kathryn J. Swoboda, Jennifer M. Kwon, Craig M. Zaidman, Claudia A. Chiriboga, Susan T. Iannaccone, Jena M. Krueger, Julie A. Parsons, Perry B. Shieh, Sarah Kavanagh, Sitra Tauscher-Wisniewski, Bryan E. McGill, Thomas A. Macek
SPR1NT (NCT03505099) was a Phase III, multicenter, single-arm study to investigate the efficacy and safety of onasemnogene abeparvovec for presymptomatic children with biallelic SMN1 mutations treated at ≤6 weeks of life. Here, we report final results for 14 children with two copies of SMN2, expected to develop spinal muscular atrophy (SMA) type 1. Efficacy was compared with a matched Pediatric Neuromuscular Clinical Research natural-history cohort (n = 23). All 14 enrolled infants sat independently for ≥30 seconds at any visit ≤18 months (Bayley-III item #26; P < 0.001; 11 within the normal developmental window). All survived without permanent ventilation at 14 months as per protocol; 13 maintained body weight (≥3rd WHO percentile) through 18 months. No child used nutritional or respiratory support. No serious adverse events were considered related to treatment by the investigator. Onasemnogene abeparvovec was effective and well-tolerated for children expected to develop SMA type 1, highlighting the urgency for universal newborn screening.
Authors: Kevin A. Strauss, Michelle A. Farrar, Francesco Muntoni, Kayoko Saito, Jerry R. Mendell, Laurent Servais, Hugh J. McMillan, Richard S. Finkel, Kathryn J. Swoboda, Jennifer M. Kwon, Craig M. Zaidman, Claudia A. Chiriboga, Susan T. Iannaccone, Jena M. Krueger, Julie A. Parsons, Perry B. Shieh, Sarah Kavanagh, Melissa Wigderson, Sitra Tauscher-Wisniewski, Bryan E. McGill, Thomas A. Macek
Most children with biallelic SMN1 deletions and three SMN2 copies develop spinal muscular atrophy (SMA) type 2. SPR1NT (NCT03505099), a Phase III, multicenter, single-arm trial, investigated the efficacy and safety of onasemnogene abeparvovec for presymptomatic children with biallelic SMN1 mutations treated within six postnatal weeks. Of 15 children with three SMN2 copies treated before symptom onset, all stood independently before 24 months (P < 0.0001; 14 within normal developmental window), and 14 walked independently (P < 0.0001; 11 within normal developmental window). All survived without permanent ventilation at 14 months; ten (67%) maintained body weight (≥3rd WHO percentile) without feeding support through 24 months; and none required nutritional or respiratory support. No serious adverse events were considered treatment-related by the investigator. Onasemnogene abeparvovec was effective and well-tolerated for presymptomatic infants at risk of SMA type 2, underscoring the urgency of early identification and intervention.
Authors: Vikram K Raghu, Steven F Dobrowolski, Rakesh Sindhi, Kevin A Strauss, George V Mazariegos, Jerry Vockley, Kyle Soltys
Classical phenylketonuria (PKU) presents a unique challenge for women of child-bearing age. In the context of pregnancy, poorly controlled hyperphenylalaninemia can result in a devastating constellation of outcomes for the baby referred to as the maternal PKU Syndrome. We present the case of a woman with classical PKU unable to maintain a restricted diet and refractory to pharmacological therapies. She elected to undergo a domino liver transplant, receiving an organ from a donor with classical branched chain ketoacid dehydrogenase deficiency (maple syrup urine disease). Plasma phenylalanine concentrations normalized within a few days after transplant and remained so on an unrestricted diet during the first year of follow-up. The patient reports subjective improvements in mood, energy level, and overall quality of life. In the appropriate clinical setting, liver transplant should be considered to provide metabolic stability for PKU patients, particularly women of childbearing age.
Authors: Megan T Lynch, Kristin A Maloney, Toni I Pollin, Elizabeth A Streeten, Erik G Puffenberger, Kevin A Strauss, Regeneron Genetics Center, Alan R Shuldiner, Braxton D Mitchell
Genetically isolated populations that arise due to recent bottleneck events have reduced genetic variation reflecting the common set of founders. Increased genetic relatedness among members of isolated populations puts them at increased risk for some recessive disorders that are rare in outbred populations. To assess the burden on reproductive health, we compared frequencies of adverse reproductive outcomes between Amish couples who were both heterozygous carriers of a highly penetrant pathogenic or likely pathogenic variant and noncarrier couples from the same Amish community. In addition, we evaluated whether overall genetic relatedness of parents was associated with reproductive outcomes. Of the 1824 couples included in our study, 11.1% were at risk of producing a child with an autosomal recessive disorder. Carrier couples reported a lower number of miscarriages compared to noncarrier couples (p = 0.02), although the number of stillbirths (p = 0.3), live births (p = 0.9), and number of pregnancies (p = 0.9) did not differ significantly between groups. In contrast, higher overall relatedness between spouses was positively correlated with number of live births (p < 0.0001), pregnancies (p < 0.0001), and stillbirths (p = 0.03), although not with the number of miscarriages (p = 0.4). These results highlight a complex association between relatedness of parents and reproductive health outcomes in this community.
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Our clinic serves as a trusted medical home for families working to prevent and treat genetic illness in their children. Serving predominantly Amish and Mennonite families, the sturdy, timber-framed building was "raised" by the hands of those in the Anabaptist community outside of Strasburg, PA. Inside the clinic is filled with an array of high-tech gene sequencing that allows us to deliver state of the art care in a nurturing environment.