Interconnected

There is a very special connection that human beings share with nature. It is a well-established fact that nature helps people relax, recharge, and even remedy many diseases. What is lesser-known, however, is that nature may also yield answers to pressing medical questions.

In the last few decades, studies of maize genes have proven to be of a significant value to biomedical research, linking the genetic information found in a kernel of corn to understanding human cell mutations responsible for various illnesses. To deepen the knowledge of maize genetics with relevance to the etiology of human diseases, Shailesh Lal, Ph.D., professor and chair of the Department of Bioengineering, is leading breakthrough research on RNA Binding Motif Protein 48 (RBM48) gene, found in corn, and its connection to human cancer.

Corn is the most economically important plant in the U.S., so, even on its own, understanding the genes employed in the development of kernels can improve human ability to genetically engineer the crop in the future. Yet, perhaps the most far-reaching benefit that corn research offers is its potential for gaining considerable biomedical insights.

Dr. Lal encountered this phenomenon first-hand a few years ago while he was studying RBM48 in corn. His observations of the gene showed its importance to the normal development of maize.

“If for some reason this gene gets destroyed, the kernel experiences significant mutations. What I also noticed is that the tissue of the developing defective kernel exhibited the same abnormal and proliferative growth as the tissue of cancerous cells in humans,” Dr. Lal explains.

Since a ortholog to the corn gene can also exist in humans, Dr. Lal initially expanded the scope of his query by inviting his colleagues to become principal investigators on his research team. The team included Dr. Gerard Madlambayan, associate professor of biological sciences, who specializes in cancer research, and Dr. Randal Westrick, assistant professor of biological sciences, whose expertise is in mammalian genome-editing technology.

Together, along with collaborators from the University of Florida and a number of OU’s graduate and undergraduate students, the group conducted research that led to discovery of a master gene that regulates the expression of other genes involved in the development of corn kernels.

Working in Dr. Westrick’s and Dr. Lal’s laboratories respectively, doctoral students Amy Siebert-McKenzie and Jacob Corll realized the similarities between a maize gene RBM48 and its human counterpart, requiring further interdisciplinary investigation.

Led by Dr. Lal, the researchers used CRISPR/Cas9 — a novel in vivo gene editing system — to mediate ablation of RBM48 in the human leukemic cell line K562 to explore the genetic function of RBM48. Utilizing RNA-seq analysis, technology for detection of gene expression, the team compared wild-type and mutant K-562 genotypes. The results showed that 48% of minor-intron-containing genes had significant U12-type intron retention in RBM48 mutants.

Genes’ protein coding sequences are broken into smaller pieces, exons, which are separated by non-coding sequences, introns. When genes are transcribed, exons and introns are included in the initial messenger RNA products. However, introns are removed during the process called splicing, so only exons are included in the mature mRNA and used to dictate what proteins are produced.

“U12-type, or minor, introns exist in most multicellular eukaryotes and constitute ∼0.5% of all introns in species with a minor spliceosome. Mutations, disrupting U12 splicing cause developmental defects in both plants and animals, are associated with myelodysplastic syndrome, predisposing individuals to acute myeloid leukemia,” Dr. Lal says.

The results of this study, published in Genetics, a flagship journal for American Genetics Society, provide tangible evidence that the primary defect of human RBM48 mutants is aberrant U12-type intron splicing. In addition, comparison of human and maize RNA-seq data, helped pinpoint genes that are likely to mediate mutant phenotypes of U12-type splicing defects.

“Our finding suggests that mutations in the RBM48 gene could play a role in the disease processes. As loss of RBM48 alters the splicing landscape of the genome, the similarities in mutant phenotypes and the conservation of genes in both humans and maize may provide a roadmap to help navigate how these disease processes occur,” states Dr. Amy Siebert-McKenzie, currently a postdoctoral fellow at Blood Research Institute at Versiti.

This groundbreaking research was supported by the National Science Foundation, the National Heart Lung and Blood Institute at National Institutes of Health, the National Cancer Institute at the National Institutes of Health, the Oakland University Research Excellence Fund, and American Heart Association Innovative Research Grant.

The collaboration highlights the ongoing interdisciplinary research, which, in addition to connecting three different OU laboratories in a successful investigative effort of bridging basic science between plants and humans, underscores the interconnectedness of all biological species. It also creates new promising avenues for exciting research opportunities. To contribute or learn more about this research, contact Dr. Lal at [email protected]