Go/* Re/* sa/sa
(Other curly coat genotypes besides Re/*: dominant Caracul, Ca/* and recessives fuzzy, fz/fz and frizzy, fr/fr. This text refers to Re/*.)

"Coat to be as curly as possible. Whiskers curly. The mouse's coat straightens somewhat as the mouse ages." (Standards for Astrex.)

Breeding information below the pictures.

	SHA Cream doe Rapunzel's Sanctuary b, o. & pic: Anniina Tuura
	SHA Red doe Knuspergardens Hippy Shake b: Maiju Collan, o: Nanna Erkkilä & Jenita Lessig Pic: Arttu Väisälä This older female has lost some of the curliness.

Quick Look

Of all curly coated breeds, Short Hair Astrex is the rarest in shows and by far the most difficult to breed right. The ideal SHA would have a distinctively short and curly coat. In reality, most SHA mice look more like shaggy short hairs.

Genetic Background

The most common genotype of an Astrex mouse is Re/*. The scientific name of the locus in question is “rex” and the symbol is “Re”. This dominant gene is a spontaneous mutation and it is located in chromosome 11. Being dominant, both Re/re and Re/Re produces curly coat. However, homozygous mice show more curl, especially youngsters. The coat gradually straightens with age, while whiskers and guard hairs remain wavy.

Mice have several curly coat genes, with differing effects. What is available to a mouse fancier varies from one location to another. As this is “Finnmouse's Site” and the most common and only truly showable astrex variety in Finland being Re/*, this is what thi article mostly deals with. That said, Caraculs (Ca/*) have re-emerged after being absent for many years.

In More Practical Terms...

The major problem with breeding short hair astrex mice is the tendency of the coat to straighten as the mouse ages. At its worse, this means the mouse has lost all distinctive curls / waves when it gets old enough to attend the first shows (in Finland, the mouse has to be 2 months or over). Astrexes can also lack in type and size.

Astrex mice are best bred as their own line along with a line of Short Hair mice specially bred with Short Hair Astrexes. This helps to build the proper modifiers so that the coat gets curlier after a few generations and the curls last longer. Unfortunately one can't really keep a “pure” Astrex-line with the Re-gene, as continuous Astrex to Astrex matings tend to make the coat sparse.

Astrex looks better on satin than without satin, so SHAs have never as good a curl as SHSAs. This is because the hollow satin hairs are soften and thus the coat gets curlier. With breeding Astrexes, one should note that there are reports on longer Re/* x Re/* -breeding causing sparser hair, so this is something to look out for. Being dominant, one does not need Astrexes to be homozygous (Re/Re) and mice with sparse coat can be left out of breeding.

As with all other varieties, with Astrex the key words are Planned breeding aiming to a set Goal. Always bear in mind that the fancy mouse is an "entirety" - breeding for a certain quality does not mean that you can forget the health, tractability, size and type of the mouse!

When it comes to varieties, a breeder who wants to be able to concentrate on the best possible coat, might want to breed astrexes in Pink Eyed White. Of course, in practice there are only few breeders who choose this option, and there's nothing inherently wrong with that decision – there's simply more to look out for in selective breeding. However, some varieties are quite difficult to get right with astrex coat, others downright suffer from the curliness.

Self varieties keep their looks on curly coat the best. With almost all other varieties the curly coat tends to make the colour appear to be poorer than it is in reality. For example, with the ticked varieties, curls cause the undercolour to show through strongly enough to make the mouse look “messy”. Of course, the judges should be able to take into consideration the effect of the coat variety on any given colour.

Caracul

Caracul is a gene (locus...) with 16 alleles (genes...) situated in chromosome 15. The official name of this gene is “keratin 71” and symbol “Krt71”. The one allele available within the mouse fancy is “Krt71^Ca”, caracul. Even though the gene is a semidominant, both homozygous and heterozygous forms look alike.

Alone, without other curly coat genes present, caracul produces poor curls. Young caracul mice have wavy coat and curved whiskers, but the waves begin to straighten already at four weeks of age. Adult caraculs look “plushy”. Characteristic feature for caracul is a “kink” at the tip of the hair.

While caracul alone gets you nowhere, combined with Re it gives you something to work with. Apparently, it works as a counter-active agent to Re:s tendency of producing sparser coat and adds a little to the overall curliness of the coat. As Ca softens the coat somewhat, it helps the curls brought on by Re to show a little better as well.

Other Curly Coat Genes?

- fuzzy (fz), spontaneous recessive, chromosome 1. fz produces thin, but very curly coat, that gets thicker and curlier with each successive moult.

- frizzy (fr), spontaneous recessive, chromosome 7. The coat starts out as short and rough, turning into short and sparse on older mice.

- Caracul-like (cal). Spontaneous dominant, chromosome 15. As the name suggests, the gene acts like caracul; youngsters are curly, but the coat looks almost completely straight by eight weeks of age.

- Caracul-like 2 – Caracul-like 7 (Cal2 – Cal7). Six genes situated in chromosome 15, all resembling caracul-like in action. Some of these genes produce coats that keep their curls longer than others. Cal7 differs from the rest by lightening the colour of eyes, ears, feet, tail and coat as well.

- crimpy (cpy). Spontaneous recessive, chromosome 15. Homozygotes have wavy, plushy looking coat and wavy whisers. No information on how well the coat keeps was available at the time of writing.