A brightly striped aquarium fish is giving scientists a peep into the mysteries of the human body. Indian and western scientists are now taking keen interest in the zebra fish a popular aquarium fish. Scientists say the genes of humans and zebra fish found in India and Pakistan — is 80% similar.
Centre for Cellular and Molecular Biology (CCMB) Hyderabad recently set up a state-of-the-art zebra fish research facility. Scientist Dr Rakesh Mishra, who heads the CCMB, said the fish has gained tremendous international prominence as a model organism.
Speaking to TOI, Dr Mishra said, “Thousands of genes between humans and the zebra fish are similar and using this fish for scientific studies has several advantages. Its embryo is transparent and hence we can actually see the body being formed. It is found all over India and breeds throughout the year making it readily available. It is known for its high fecundity (mature females lay several hundred eggs at weekly intervals) and short generation time (3-4 months). The embryo also develops completely in 48-72 hours because of which experiments can be completed very fast.”
The team is now working to see how the body of the zebra fish forms which could ultimately tell us how humans develop from a single cell and the mechanism in which “the anterior and posterior” is decided.
Dr Mishra said, “We are going to replace the genes of zebra fish with that of humans to see how it behaves. We are beginning by studying how embryonic development begins with a single cell and then divides to result in a body pattern. We want to study the mechanism that controls the expression of homeotic genes which control formation of anterior and posterior body axis.”
Zebra fish, unlike humans, can regenerate their spinal cord following injury. Scientists are now trying to see how they do it and whether humans can replicate such an action.
Yona Goldshmit, a scientist working at Monash University in Australia, is also studying the mechanism of spinal cord repair in zebra fish. She recently described a protein that may be a key difference between regeneration in fish and mammals. One of the major barriers to spinal regeneration in mammals is a natural protective mechanism, which incongruously results in an unfortunate side effect.
After a spinal injury, nervous system cells called glia are activated and flood the area to seal the wound to protect the brain and spinal cord. In doing so, however, the glia create scar tissue that act as a physical and chemical barrier, which prevent new nerves from growing through the injury site, she said.
One striking difference between the glial cells in mammals and fish is the resulting shape: mammalian glia take on highly branched, star-like arrangements that appear to intertwine into dense tissue. Fish glia cells, by contrast, adopt a simple elongated shape – called bipolar morphology – that bridges the injury site and appears to help new nerve cells grow through the damaged area to heal the spinal cord.
“Zebra fish don’t have so much inflammation and the injury is not so severe as in mammals, so we can actually see the pro-regenerative effects that can happen,” Goldshmit explained.
Spinal muscular atrophy (SMA) is a group of progressive neurodegenerative diseases that affect the nerves in the spinal cord that control muscles, leading to weakness, movement difficulties, poor posture and trouble breathing and eating. Scientists are using the zebra fish to study a cure for this.
Researchers from the University of Pittsburgh are using zebra fish to study the biological mechanisms that lead to intestinal inflammation, providing additional understanding that may allow development of better therapies.
Prakash Thakur, a research associate, described a mutant zebra fish strain that shows many pathological characteristics, including inflammation, abnormal villous architecture, disorganized epithelial cells, increased bacterial growth and high numbers of dying cells in the intestine. “Most of the hallmark features of the disease are seen in this mutant. We are utilizing this fish as a tool to unravel fundamental mechanisms of intestinal pathologies that may contribute to intestinal inflammatory disorders,” Thakur said.
Human acute T-cell lymphoblastic leukemias (ALL) and lymphomas (LBL) have high relapse rates in pediatric patients and high mortality rates in adults. Hui Feng at Boston University School of Medicine is using a zebra fish model of leukemia to search for promising targets for new molecular treatments for these diseases.
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