The work of a Japanese-led international scientific consortium on the development of a method for identifying genes hidden in large genome sequences is described in the latest issue of the scientific journal Nature, which is released today.

The consortium, headed by Yoshihide Hayashizaki of the RIKEN Genomic Sciences Center Yokohama in Kanagawa Prefecture, has analyzed more than 20,000 strands of mouse DNA in order to clarify the function of the gene they represent, it has announced.

The magazine will detail the first chapter of their Mouse Gene Encyclopedia Project.

Sequencing the human genome has produced a vast string of mixed-up, repetitive code, mostly nonsense "junk" DNA, in which genes are hidden like pearls on the ocean floor, the researchers said.

Knowing the DNA sequence alone is no good unless it is known which bits are genes are which bits are junk. The RIKEN method, developed using the mouse genome, is expected to help identify genes in the human genome, according to the consortium.

Genes have their effects -- they are expressed -- when they are copied into RNA, and delivered into the cell where they make proteins. RIKEN's mouse project collected the strands of this messenger RNA produced when a gene is expressed and used these to clone the complementary DNA strand.

There are 3 billion nucleotide units in the human genome and estimates of the number of genes it contains vary from 30,000 to 120,000. The uncertainty and the junk DNA has made decoding the sequence unreliable.

Like the human genome, the mouse genome is composed of large stretches of junk DNA, so methods for finding genes in mice will help researchers also find them in the human sequence. The RIKEN collection of cDNA clones is one of the largest described for any organism, the consortium said.

By comparing the mouse cDNA strands with each other, and with known genes in other species, the groups were able to deduce what the cDNA strands actually do, and hence locate genes. The consortium has found over 100 new genes representing metabolic enzymes and 10 genes very similar to those that cause human diseases, it said.