Can the product of the theta gene be a real globin?

The article explores the potential for the product of the theta gene to be a real globin. It indicates that while some species show signs of the possibility, the predicted amino acid sequence suggests a non-viable ‘globin’ product.

Research Context

• The study delves into a newly discovered member of the alpha-globin gene family identified in several species, known as the theta 1 or psi alpha gene.
• In higher primates, this gene appears to possess all necessary structural features for expression and has seemingly been under significant selective constraints, suggesting that the gene might be functional or could recently have been functional. However, no corresponding ‘globin’ has yet been recognized.

Study Findings on Different Species

• In galagos and rabbits, the theta 1 and psi alpha genes have accumulated enough inactivating mutations to classify them as pseudogenes, which means they’re genomic DNA sequences similar to normal genes but are non-functional.
• Horses also possess an alpha-like gene (psi alpha) positioned similarly to other species in relation to functional alpha genes, indicating possible functionality. However, the predicted amino-acid sequences hint at a non-viable ‘globin’ product due to severe deleterious amino-acid replacements.

Evolutionary Insights

• Some of these amino-acid changes are seen across rabbit and primate sequences, signifying they predate the mammalian radiation – the rapid diversification of mammals that occurred around 66 million years ago in the Cenozoic Era.
• This widespread presence suggests that if any of these genes are still functional, they likely do not produce haemoglobin – a protein in red blood cells that carries oxygen.

Conclusion

• The research raises doubts about the functionality of the theta gene in producing viable globin, suggesting further investigation and comparative analysis across different species is needed to fully understand the patterns of these genetic sequences.