Ruminants genome no longer contains Whey Acidic Protein gene but only a pseudogene.
Whey Acidic Protein (WAP) has been identified in the milk of only a few species, including mouse, rat, rabbit, camel, pig, tammar wallaby, brushtail possum, echidna and platypus. Despite intensive studies, it has not yet been found in the milk of Ruminants. We have isolated and characterized genomic WAP clones from ewe, goat and cow, identified their chromosomal localization and examined the expression of the endogenous WAP sequence in the mammary glands of all three species. The WAP sequences were localized on chromosome 4 (4q26) as expected from comparative mapping data. The three ruminant WAP sequences reveal the same deletion of a nucleotide at the end of the first exon when compared with the pig sequence. Due to this frameshift mutation, the putative proteins encoded by these sequences do not harbor the features of a usual WAP protein with two four-disulfide core domains. Moreover, RT-PCR experiments have shown that these sequences are not transcribed and are, thus, pseudogenes. This loss of functionality of the gene in Ruminants raises the question of the biological role of the WAP. Some putative roles previously suggested for WAP are discussed.
Laboratoire de Biologie du Développement et de la Reproduction, Institut National de la Recherche Agronomique (INRA), 78352 Jouy-en-Josas Cedex, France.
Siham
S
Hajjoubi
Sylvie
S
Rival-Gervier
Hélène
H
Hayes
Sandrine
S
Floriot
André
A
Eggen
François
F
Piumi
Patrick
P
Chardon
Louis-Marie
LM
Houdebine
Dominique
D
Thépot
D000818:Animals; D001483:Base Sequence; D002875:Chromosomes / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D016368:Frameshift Mutation; D005786:Gene Expression Regulation / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000378:metabolism; D008894:Milk Proteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D011544:Pseudogenes / Q000235:genetics*; D012418:Ruminants / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid
D008894:Milk Proteins; C024471:whey acidic proteins