Critical for B-cell development. Associates non-covalently with VPREB1 (PubMed:17431183). Interacts with SYNV1/HRD1 (via N-terminus); this interaction leads to increased IGLL1 ubiquitination and degradation in pre-B cells, possibly through a lysosomal, not proteasomal, pathway (By similarity). In pre-B cells, localizes predominantly to the endoplasmic reticulum. Expressed only in pre-B-cells and a special B-cell line (which is surface Ig negative). The disease is caused by variants affecting the gene represented in this entry. IGLL1 mutation db IGLL1