This transgene consists of a 5.5kb fragment of the mouse Myhca gene including 4.5kb of 5' sequence plus exons 1 - 3 of the 5' untranslated region driving expression of the open reading frame of the canine SLC8A1 gene. Expression is primarily seen in the heart with low levels of expression detected in the lung and in one line in the brain. Eight lines were generated, designated A through H, that all have identical phenotype. This is a representative record for all 8 lines.