. 2004 Aug 13;5(9):R67. doi: 10.1186/gb-2004-5-9-r67

Table 7.

Occurrence of CKI-family members in different vertebrate species

	Human	Zebrafish	Fugu	Xenopus tropicalis	Ambystoma mexicanum
CDKN1A (p21)	+	-*	+	+	-*
CDKN1B (p27^Kip1)	+	+	+	-^†	+
CDKN1C (p57)	+	+	+	-^†	+
p28^Kix1	-	-	-	+^‡	+^‡

* Genes most likely present, yet not identified due to limited sequence information; † genes not present in genomic sequence information; ‡ genes so far only present in amphibian species. Databases searched were the human, mouse, rat, fugu, zebrafish and X. tropicalis genome databases, and the EST databases for X. laevis, X. tropicalis, zebrafish, A. mexicanum and A. tigrinum.