Hirschsprung disease is a devastating condition that affects newborns, leaving them with a blocked intestine and an inability to pass stool. But what if a simple change in our genetic code could be the culprit? A groundbreaking study has uncovered a new way to understand this mysterious disease, and it's all about the genes.
During the development of our digestive system, a complex network of nerves, known as the enteric nervous system (ENS), forms around it. This 'second brain' controls the movement of food and waste through our gut. However, when certain genetic instructions are altered, these nerves may fail to develop properly, resulting in Hirschsprung disease (HSCR).
But here's where it gets fascinating: Previous animal models of HSCR focused on individual genes, but a team of researchers from NYU Langone Health has developed a multi-gene mouse model that more accurately represents the human disease. This new approach considers the interactions between multiple genes, providing a more comprehensive understanding of HSCR.
"We now have a powerful tool to study Hirschsprung disease that brings us closer to the human experience of the disorder," said Ryan Fine, PhD, the study's first author and postdoctoral fellow at the Center for Human Genetics and Genomics. "Our research reveals how specific mutations in multiple genes collaborate to disrupt the development of the intestinal nervous system."
The study, led by the renowned Aravinda Chakravarti, PhD, builds upon his 30 years of research on HSCR. Chakravarti was instrumental in identifying the two primary genes associated with the disease: RET and EDNRB. In previous studies, researchers would 'knock out' these genes, completely destroying their function, which only partially mimicked the human disease.
And this is the part most models missed: In humans, HSCR is four times more common in males and primarily affects the lower regions of the colon. However, in the knockout mice, the disease incidence was similar between genders, and the entire colon and small intestine were affected.
The new study, published in PNAS, introduces a more nuanced approach. By creating different combinations of weaker mutations in both RET and EDNRB genes, the researchers achieved a more realistic model. In the most successful combination, only one copy of RET was knocked out, while both copies of EDNRB remained partially functional, resulting in a model that closely replicated human symptoms.
The researchers also uncovered a surprising molecular detail. HSCR is thought to be caused by a lack of nerve cells in the gut, but the HSCR mice had an abundance of immature neural cells (progenitor cells) during development. This led the team to investigate further, and they found that the SOX2OT gene, which controls the maturation of neural progenitor cells, was significantly increased in HSCR mice.
A controversial interpretation: Without fully functional RET and EDNRB genes to regulate it, SOX2OT may interfere with the maturation process, preventing the development of a complete ENS. This finding opens up new avenues for understanding HSCR and potentially other developmental disorders.
Chakravarti believes this multi-gene approach could revolutionize the study of complex human disorders. "By mimicking the way these diseases occur in humans, with multiple small mutations across genes, we can uncover the intricate details of these conditions and develop more effective treatments," he said.
This study not only provides a more accurate model of HSCR but also highlights the importance of considering gene interactions in disease research. It invites further discussion on the potential of multi-gene models to enhance our understanding of complex disorders and the development of targeted therapies.
