Scientists in Sweden recovered RNA from extinct, 130 year old Tasmanian Tiger, also famous as thylacine.
They trace with genres were active in tissues.
The study was led by DR Marc R Friedlander at Stockholm University in sweden will help from nearby research centers.
His work stresses on RNA biology and gene regulation in cells specially the tiny regulation that shape development.
DNA
RNA usually breaks apart faster than DNA so most old samples lose their transcriptome the full set of RNA message from those tissues.
Dry storage can slow chemical reactions that chew up RNA and museum skins sometimes hold more than expected.
A 2019 paper showed RNA can survive in permafrost and old wolf skins long enough to regain tissue signals.
Thylacine, RNA, and tissue
The thylacine was marsupial predator with pouch that vanish after hunting and habitat loss.
Specimen sat dried at room temperature in Swedish museum and it provided skin and muscle tissue for sequencing.
To avoid modern contamination the team worked in clean rooms built for ancient molecules and tracked possible human handling.
Proving the RNA was from a thylacine
How could anyone be sure this RNA came from thylacine and not from modern contaminant?
Thylacine genome and human sequences appeared at lower levels that fit museum handling.
They also use metatranscriptomics which is way of scanning all RNA to identify species and microbes to separate thylacine fragment from contaminants.
Chemical scars called deamination damage that changes one RNA letter into other rose near fragment ends as expected.
In muscle the strongest signals cames from genes tied to contraction and energy use including huge protein titin.
The RNA profile pointed to slow muscle fibers which fit the location where researchers took tissue from near the shoulder blade.
They detected text involved in oxygen storage and fuel recycling hints about how those cells worked when alive.
With millions of fragments the team capture only small slice of the full muscle transcriptome so signal stayed quiet.
RNA and thylacine Skin samples
Skin samples carried many RNA fragments from keratin genes matching the outer layer that protects animals from wear.
Two skin section contained hemoglobin RNA a sing of blood left in tissue when the specimen was prepared.
Skin sits on outside it can pick up microbes layer thylacine reads still dominated the data.
When the team compared these profiles with living marsupials and dogs skin looked like skin and muscle looked like muscle.
MicroRNAs: The small regulators
MicroRNAs, short RNAs that tune how much protein a gene makes often run about 22 building blocks long.
RNA evidence confirmed a thylacine specific microRNA form showing how gene regulation can differ even between close relatives.
These small regulators varied sharply between skin and muscle giving other check that sequences came from right tissues.
Fixing the thylacine genome map
Scientist use annotation labeling genes on genome map to turn raw DNA into usable reference for biology.
RNA comes from finished messages it can expose mission exons and patch gaps that confuse DNA only gene lists.
In the thylacine RNA data pointed to location of ribosomal RNA genes that were absent from assemblies.
Source
The story is published in Genome Research
