Illustration of Cells and Mice (IMAGE) Karolinska Institutet Caption In the embryonic spinal cord, progenitor cells express various genes that determine their final cell specificity. In normal mice (top image) some nerve cells express the genes Dbx1 (red), E1Ngn2 (green), or both (yellow). When walking, animals move their left and right limbs in alternation. In contrast, when animals were genetically engineered to lack the nerve cells co-expressing Dbx1 and E1Ngn2 (bottom image, note absence of yellow cells), their walking gait was changed to a complete rabbit-like hopping, with the left and right limbs moving in synchrony. Credit Julien Bouvier Usage Restrictions May only be published in connection to news reports about the current findings (<i>Nature</i>, June 30, 2013) License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.