Tissue Specific Expression of Neurofibromin Isoforms in Swine
Authors: Schomberg Dominic T. , Rubinstein Clifford Dustin , Meudt Jennifer J. , Shanmuganayagam Dhanansayan 
Published: June 2021

Neurofibromatosis type 1 (NF1) is one of the most common monogenic disorders and affects 1 in 2,500 children. The disorder manifests in varying, complex phenotypes that include cognitive and learning dysfunction, bone and cardiovascular disorders, and an increased risk of developing benign and malignant nervous system tumors. The neurofibromin gene contains 63 exons, of which four are alternatively spliced (optionally included) within isoforms of neurofibromin transcripts that are differentially expressed in specific tissues. Recently, several swine models of NF1 have been developed in hopes that these models will recapitulate the disorder in humans better than existing rodent models and thus offer a more translational platform for the development of novel therapies. However, the normal expression patter of neurofibromin isoforms in swine is unknown. In the current study, we characterize the tissue specific expression pattern of neurofibromin in swine to enable comparisons to that known in humans.Tissue samples taken from the cortex, cerebellum, pituitary, amygdala, hippocampus, substantia nigra, optic nerve, brachial nerve, adipose, skeletal muscle, small intestine, and colon of swine were used to determine mRNA expression levels for isoforms containing each of the four known alternatively spliced exons (ASEs). Mesenchymal stem cells isolated and cultured from adipose tissue were also included in the analysis. A standard qPCR approach was first used to determine in which tissues ASEs significantly varied. Then, droplet digital PCR was used to produce a more precise analysis of ASE expression pattern in targeted tissues. The level of total neurofibromin mRNA and the relative expression of each of the four ASEs were determined in the cultured MSCs and each tissue sample. The stem cells were found to have the highest expression of total neurofibromin mRNA, while nervous tissues containing gray matter and white matter showed 2‐ and 6‐ fold lower expression, respectively. Muscle tissue showed 14‐fold lower expression. Muscle and gray matter tissues had the highest relative expression of ASE 12 (a12), while the stem cells and white matter tissues had the highest relative expression of ASE 31 (a31). Muscle showed the most relative abundance of ASE 57 (a57). The expression of a12 and a57 were negligible in stem cells. Most malignant NF1 tumors originate from white matter and in this tissue, we observed higher relative levels of a31, an ASE that is known to influence Ras activity implicated in tumorigenesis. Overarchingly, our results are concordant with known patterns of ASE expression in corresponding human tissues and provide the first characterization of neurofibromin ASE expression in swine.Support or Funding InformationThe research was supported by the Biomedical & Genomic Research Group Discretionary Fund (University of Wisconsin‐ Madison), NF North Central, NF Network, and NF Team Foundation.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.