A team of researchers identified a gene that might serve as a molecular intersection between our mood and the biological, or circadian, clock that determines when we are awake and when we sleep. In other words, a gene that makes us grumpy if we stay up late and don't get enough sleep.
http://www.psypost.org/2016/02/clock-gene-may-connect-mood-and-sleep-41158
http://www.psypost.org/2016/02/clock-gene-may-connect-mood-and-sleep-41158