Graduation Date

Spring 2022

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Amy Sprowles, Ph.D.

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Fernando Fierro, Ph.D.

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Brigitte Blackman, Ph.D.

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Catalina Cuellar-Gempeler, Ph.D.

Fourth Committee Member Affiliation

HSU Faculty or Staff

Subject Categories



Snyder-Robinson Syndrome (SRS), an X-linked intellectual disability that arises in children, exhibits debilitating phenotypes like severe osteoporosis. These patients demonstrate an inability to produce mineralized new bone in comparison to the rate at which bone is resorbed, thus leading to weaker skeletal structure and atraumatic fractures. The known cause of SRS is due to loss-of-function mutations within the gene that encodes Spermine Synthase (SMS). Loss of SMS enzymatic activity, which catalyzes the conversion of polyamines spermidine into spermine, demonstrates an increase in the spermidine/spermine ratio in all documented cases of this disorder. The involvement of polyamines in osteogenesis is still not well understood, but it is apparent that maintaining strict regulation of these organic compounds is necessary for bone mineralization. Due to deficient therapeutic intervention, it is imperative to continue researching the molecular mechanisms by which the polyamine pathway regulates bone mineralization. Here we investigated the effects of exogenous supplementation of either putrescine, spermidine, or spermine throughout osteogenic differentiation within healthy human bone-marrow derived mesenchymal stromal cells (MSCs). Through this, we confirmed the ability to transport polyamines within MSCs, as well as observed inhibitory effects throughout osteogenesis. We found that excess spermidine inhibits alkaline phosphatase activity, an important osteogenic marker, while excess spermine decreases hydroxyapatite synthesis as confirmed through Alizarin red S staining. Furthermore, we observed the gene that encodes spermidine/spermine N1-acetyltransferase 1 (SAT1) depicts a powerful upregulation in expression at the mRNA level during osteogenic differentiation in healthy MSCs. To further explore this, we silenced SAT1 expression using lentiviral vectors expressing a SAT1-specific shRNA. Our preliminary studies suggest that suppressing SAT1 expression has minimal effect on osteogenesis. These data suggest that the conversion of higher polyamines into more easily excretable lower polyamines is necessary in bone development, and altogether, our studies propose that SRS is due to the accumulating spermidine interactions within cells throughout osteogenesis.

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