 On the contrary, Nf1 heterozygous animals ("Nf1+/-") were viable but predisposed to form different types of tumors.In some of these tumor cells, genetic events of loss of heterozygosity (LOH) were observed, supporting that NF1 functions as a tumor suppressor gene.A conditional knockout mouse line, called "Nf1tm1a(KOMP)Wtsi" was later generated as part of the International Knockout Mouse Consortium program, a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists.