RXR sequenced, now on to imposex

Samera Mulatu, Georgia Southern University

IMG-0640Findings: My experience at the Fort Johnson REU Program was phenomenal! Towards the end of the program, I was able to retrieve the RXR gene sequences for the Eastern mud snail. While working towards this goal, I was able to get a first hand glimpse of the long and hard steps and techniques taken to retrieve DNA sequences. From generating primers, doing dissections, extracting RNA, making cDNA, and even making PCR products, these listed skills are only just a short list of what I learned during this research experience. Retrieving the RXR gene sequences for the mud snail, was a trial and error process. Sequences were sent in at least five times, and four of those five times did not give good results. This was a big lesson for me, and reminded me that science is a trial and error process because all of it is a learning process.

Now that the RXR gene sequence for the Eastern mud snail was retrieved, the next steps in this project would be to use the sequences to place the mud snail in its proper spot on the phylogenetic tree. Also, now that the gene sequences are retrieved they will be used next fall by Edwina Mathis (a graduate at MUSC who’s doing her research in this topic) and Dr. Demetri Spyropoulos to induce imposex in the Eastern mud snail while exposing the snails to TBT, SPAN 80, and DOSS. Afterwards, they will measure changes in isoform expression.

The significance of the results from this study will hopefully show that mud snail imposex is a sensitive indicator of endocrine disrupting compounds in the environment which may impact human health and the health of other organisms in the ecosystem. This is because high imposex rates in mud snail species could possibly be linked to higher levels of contamination found in that site within the Charleston Harbor. Hopefully this study will further future research on EDCs and their effects on different species.

I would like to give a big thank to Dr. Demetri Spyropoulos for guiding me in my research. Also to the Fort Johnson REU Program, NSF DBI- 1757899, for providing me with the funds to complete this project.

Related research

Hotchkiss, A.K, A.G.Leblanc, R.M. Sternberg. 2002. Synchronized expression of Retinoid X Receptor mRNA with Reproductive Tract Recrudescence in an Imposex- Susceptible Mollusc. Environ. Sci Technol. 42: 1345- 1351.

Ravitchandirane, V. S, M.Thangaraj. 2013. Phylogenetic Status of Babylonia Zeylanica (Family Babyloniidae) Based on 18S rRNA GENE FRAGMENT.Annals of West University of Timisoara, ser. Biology. 1(2): 135- 140.

Barron- Vivanco, B.S, D. Dominguez- Ojeda, I.M. Medina- Diaz, A.E. Rojas- Garcia, M.L. Robledo- Marenco. 2014. Exposure to tributyltin chloride induces penis and vas deferns development and increases RXR expression in females of the purple snail (Plicopurpura pansa). Invertebrate Survival Journal. 11: 204-2012.

Horiguchi, T., M. Morita, T. Nishikawa, Y. Ohta, H. Shiraishi. 2007. Retinoid X Receptor gene expression and protein content in tissues of the rock shell Thais clavigeraAquatic Toxicology. 84: 379-388.

 

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Why Cleaning our Oceans Could Also Reduce Obesity

Samera Mulatu, Georgia Southern University

The problem: Charleston Harbor is undergoing massive dredging to make way for super tankers. There are concerns that banned legacy compounds buried in the sediments, such as tributyltin (TBT), will be brought up into the harbor waters as a result of the dredging. A related concern is that oil spills will become more common and involve the release of cleanup compounds into the water column, including Span 80 and dioctyl sodium sulfosuccinate (DOSS). These three compounds and others are known to act as endocrine disrupting compounds (EDCs), which disrupt the Retinoid X Receptor (RXR) pathway. In mollusks, RXR disruption induces imposex development (when female mollusks develop male sex traits). One goal of my project is to measure the rates of imposex in the Eastern mud snail (Tritia obsoleta) within different sites in Charleston Harbor and to see if these rates increase over time with dredging.

The same chemicals that cause imposex are used in medications, processed foods (e.g. homogenized milk), textiles, paints, and cosmetics.  Because the identification and study of many EDCs is fairly new and upcoming, their effects on the human body are still not fully understood. Those EDCs found to promote weight gain are called “obesogens.” Early exposure to obesogens can detrimentally affect a child’s health into adulthood! These obesogens can persistently alter hormonal signaling pathways in children, which can lead to permanent metabolic damage.

Obesity in the United States is at an all-time high. Approximately half of the population is predicted to be obese by 2020.  This is a serious health problem because obesity can drastically increase the likelihood of developing cancer, diabetes, and heart disease. Many people associate obesity with lack of exercise. However, it should be noted that obesogens can reduce energy, increase appetite and change behaviors associated with weight gain.

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The author (right) collecting mud snails (Tritia obsoleta).  Photo: Dr. Spyropoulos.

I would like to give a big thank to Dr. Demetri Spyropoulos for guiding me in my research. Also to the Fort Johnson REU Program, NSF DBI- 1757899, for providing me with the funds to complete this project.

Related research

Hotchkiss, A.K, A.G.Leblanc, R.M. Sternberg. 2002. Synchronized expression of Retinoid X Receptor mRNA with Reproductive Tract Recrudescence in an Imposex- Susceptible Mollusc. Environ. Sci Technol. 42: 1345- 1351.

Ravitchandirane, V. S, M.Thangaraj. 2013. Phylogenetic Status of Babylonia Zeylanica (Family Babyloniidae) Based on 18S rRNA GENE FRAGMENT.Annals of West University of Timisoara, ser. Biology. 1(2): 135- 140.

Barron- Vivanco, B.S, D. Dominguez- Ojeda, I.M. Medina- Diaz, A.E. Rojas- Garcia, M.L. Robledo- Marenco. 2014. Exposure to tributyltin chloride induces penis and vas deferns development and increases RXR expression in females of the purple snail (Plicopurpura pansa). Invertebrate Survival Journal. 11: 204-2012.

Horiguchi, T., M. Morita, T. Nishikawa, Y. Ohta, H. Shiraishi. 2007. Retinoid X Receptor gene expression and protein content in tissues of the rock shell Thais clavigera. Aquatic Toxicology. 84: 379-388.