HPRT1 and hyperinsulinemic hypoglycemia, familial, 4: While mice have been used as a model animal, for example to study HGPRT deficiency [58], new models are emerging that are more prone to developmental studies due to external development such as the zebra fish [59] or Xenopus laevis (our unpublished work), or more open to the possibility of running genetic experiments (nematode, [60]).