Abstract: The present invention relates to a method of diagnosis of neonatal diabetes, congenital hypothyroidism and congenital glaucoma, comprising detecting the presence of a mutation in the GLIS3 gene and to a method for preparing functional pancreatic beta-cells by culturing human multipotent or pluripotent cells, such as embryonic stem cells (ES-cells) or human somatic stem cells in a culture medium comprising a effective amount of GLIS3 to induce said cells differenciation into functional pancreatic beta-cells producing insulin. It also relates to a pharmaceutical composition comprising GLIS3 as active ingredient.