Complex sentence: The Arntl gene is an essential and nonredundant component within the mammalian clock gene regulatory network, since it is the only gene within the mammalian circadian clock whose sole deletion in a mouse model generates arrhythmicity at both the molecular and behavioral levels.
Split into simpler sentences: The Arntl gene is an essential component within the mammalian clock gene regulatory network. It is a point of sensitivity within the network, as it is the only gene whose single knockout in a mouse model generates arrhythmicity at both the molecular and behavioral levels.