Female tsetse flies and what they teach us about mammals

Tsetse flies utilise a process similar to mammalian lactation. Image: Image modified from Benoit et al., Biol Reprod 2012.

Lactating tsetse flies can shine a light upon lactating mammals.

The dreaded tsetse fly is a bloodsucking creature that occurs only in Africa. It feeds off human and animal blood, which is rich in proteins and lipids. Every time tsetse takes a mouthful of blood, it infects its “˜meal’ with one of two germs, Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense. Both cause sleeping sickness, a diseases that affects about 60 million people in 37 countries, and nagana, a paralysing disease occurring mainly in horses and cattle.

One of the best ways to combat sleeping sickness and nagana is eliminating the tsetse fly — some efforts have included the sterilisation of male tsetse flies. A new study published in Biology of Reproduction’s Papers-in-Press reveals that by manipulating some enzymes and other milk proteins, the tsetse population could be drastically reduced.

Female tsetse flies are viviparous. Once the egg is fertilised, they ovulate it into the uterus, where the offspring develops. When the larva hatches, it remains inside the uterus and feeds off a fluid secreted by milk glands on the uterine wall. The milk contains an enzyme called sphingomyelinase (SMase), which is needed for the production of a key component of cell membranes.

Researchers from Yale University and the Slovak Academy of Sciences studied the components in the milk secretion of female tsetses, and altered its composition “by reducing the expression of genes responsible for protein that generated milk in the mother using injection of short interfering RNA,” says Josh Benoit, postdoctoral fellow at the Yale School of Public Health.

In this study the researchers reduced the levels of SMase, which greatly affected the offspring’s development and health. They researchers believe that if they manage to manipulate the levels of SMase, they could shrink the population of tsetse flies in subsaharan Africa and therefore reduce the incidence of sleeping sickness and nagana.

The lack of SMase “alters the development of juveniles by interfering with proper transfer of and digestion of sphingolipids in the developing intrauterina larva. Sphingolipids are critical for proper development and many celullar processes,” says Benoit.

This unprecedented study also shines a light on the SMase-encoding genes that cause Niemann-Pick disease, a neurodegenerative disorder that affects children and is specifically associated with SMase deficiency.

Lactation in tsetse flies and mammals have somewhat similar patterns “including lipid composition, transfer of beneficial bacteria, iron transporting protein and spihingomyelinase activity. This is not surprising since even though flies and mammals are very different, each needs similar biochemical factors during juvenile development and have similar underlying mechanism to provide these factors,” says Benoit.

Although, as Benoit suggests, there would need to be many more studies to find a cure for Niemann-Pick Disease, using tsetse flies and other insects to study diseases associated with interference in sphingolipid metabolism could facilitate the process.



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