Conservation within artiodactyls of an AATA interrupt in the IGF-I microsatellite for 19-35 million years

Occurrence of an AATA interrupt in the IGF-I microsatellite was investigate d in a number of Artiodactyl species, namely pigs. camels, deer, cattle, go ats, and sheep. Comparison of DNA sequences in the 5' flank of the microsat ellite in these species revealed that the interrupt within the microsatelli te is conserved in deer, cattle, sheep, and goats but is absent from camels and pigs. The interrupt was introduced into the Artiodactyl phylogeny afte r the divergence of the Camelidae but before the divergence of the Cervidae , and thus its time of origin can be estimated to be 19-35 MYA. In contrast to the repeat units which are hypermutable, the interrupt has been conserv ed for a very long time and may even have suppressed microsatellite variati on by inhibiting replication slippage. A 12-bp deletion in the 5' flank of the microsatellite in camels corresponds to a consensus reversed repeat in deer, cattle, sheep, and goats with unknown functional significance. Apart from this deletion, the 5' flank of the microsatellite is highly conserved in Artiodactyl species.