Furthermore, research involving rhesus monkeys has intriguingly revealed that α-motoneurons not only retain both their size and number but also age at a differing pace (Maxwell et al., 2018), a feature probably related to the intrinsic cell properties and its differential vulnerability observed in pathological conditions such as ALS or SMA (Valdez et al., 2012; Comley et al., 2015; Murray et al., 2015; Tejero et al., 2016; Nijssen et al., 2017). Here, SMN1 is linked to amyotrophic lateral sclerosis.