Dust Mites Have Unique Genome Cleaning System

A new genetic study coming out of the University of Michigan has shed light on the inner workings of the dust might genome and its novel internal protection mechanisms.

House mites can be found in almost 100% of all our houses, thriving in couches, beds and carpets of even the cleanest of homes. They are the main cause of indoor allergies, affecting more than 1.2 billion people every year.

Every animal on earth has ways of detecting, targetting and destroying ‘transposable elements’ within their gnome. The pieces of non-coding DNA can change their position in the genome and can cause mutations and disease.

In most cases, the detection of these elements is carried out by small RNA fragments that find and break these unwanted genetic sequences. This mechanism is called the Piwi-associated RNA pathway—named for the protein Piwi, first discovered in fruit flies.

This latest study took a look at the DNA and RNA of the American dust mite, Dermatophagoides farina. To their surprise, the researchers found an absence of the Piwi proteins or the small RNA fragments.

Instead, dust mites have replaced the Piwi pathway with a completely different small RNA mechanism that uses small-interfering RNAs. The dust mite genome also encodes a protein that can amplify small-interfering RNAs.

“We believe that the evolution of this novel mechanism to protect genomes from transposable elements is linked to the unusual evolution of the dust mite,” says Pavel Klimov, an associate research scientist in the ecology and evolutionary biology department at the University of Michigan and a co-author of the paper that appears in PLOS Genetics.

“These animals evolved from parasitic ancestors. Frequently, the transition to parasitism is associated with dramatic genetic changes, a legacy carried by the dust mite when it moved back to a free-living lifestyle.”

Our modern-day mites evolved over 48 to 68 million years ago and used to live in bird nests before graduation to human dwellings relatively recently from an evolutionary standpoint.

Source: University of Michigan

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