| Summary: | <p>Abstract</p> <p>Background</p> <p>The ATP-binding cassette transporter <it>ABCC6</it> gene is located on chromosome 16 between its two pseudogenes (<it>ABCC6P1</it> and <it>ABCC6P2</it>). Previously, we have shown that <it>ABCC6P1</it> is transcribed and affects <it>ABCC6</it> at the transcriptional level. In this study we aimed to determine copy number variations of <it>ABCC6, ABCC6P1</it> and <it>ABCC6P2</it> in different populations. Moreover, we sought to study the transcription pattern of <it>ABCC6</it> and <it>ABCC6</it> pseudogenes in 39 different human tissues.</p> <p>Findings</p> <p>Genomic DNA from healthy individuals from five populations, Chinese (n = 24), Middle East (n = 20), Mexicans (n = 24), Caucasians (n = 50) and Africans (n = 24), were examined for copy number variations of <it>ABCC6</it> and its pseudogenes by pyrosequencing and quantitative PCR. Copy number variation of <it>ABCC6</it> was very rare (2/142; 1.4%). However, one or three copies of <it>ABCC6P1</it> were relatively common (3% and 8%, respectively). Only one person had a single copy of <it>ABCC6P2</it> while none had three copies. In Chinese, deletions or duplications of <it>ABCC6P1</it> were more frequent than in any other population (9/24; 37.5%). The transcription pattern of <it>ABCC6P2</it> was highly similar to <it>ABCC6</it> and <it>ABCC6P1</it>, with highest transcription in liver and kidney. Interestingly, the total transcription level of pseudogenes, <it>ABCC6P1</it> + <it>ABCC6P2</it>, was higher than <it>ABCC6</it> in most tissues, including liver and kidney.</p> <p>Conclusions</p> <p>Copy number variations of the <it>ABCC6</it> pseudogenes are quite common, especially in populations of Chinese ancestry. The expression pattern of <it>ABCC6P2</it> in 39 human tissues was highly similar to that of <it>ABCC6</it> and <it>ABCC6P1</it> suggesting similar regulatory mechanisms for <it>ABCC6</it> and its pseudogenes.</p>
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