Inner nuclear membrane protein (PubMed:15035436, PubMed:24700158). May have a role in maintaining the structural integrity of the nuclear lamina (PubMed:24700158). During pupal development, plays essential and redundant functions with the other LEM domain proteins; MAN1 and Ote (PubMed:24700158). Also has a redundant but important role with Ote in larval development (PubMed:24700158). Detected in the nucleus envelope and cytoplasm. In the cytoplasm, it appears to localize to discrete foci. Predominantly expressed in the nucleoplasm with very low expression levels in the cytoplasm. Appears to be predominantly expressed in the nucleus envelope but expression is not uniform. Outside of the nucleus it is located to discrete foci which may be the endoplasmic reticulum. Uniform expression throughout development and in adults (at protein level) (PubMed:16439308). Isoform A: Expressed in larvae (PubMed:15035436). Isoform B: Lower levels of expression in larvae compared to isoform A (PubMed:15035436). Viable and fertile, with no obvious phenotype (PubMed:15035436, PubMed:24700158). In the salivary gland nuclei of third-instar larvae, there are increased deformities in the nuclear lamina with 1 to 7 abnormal O-shaped Lam-containing structures (PubMed:24700158). No significant decrease in adult survival, however double mutants with either Ote or MAN1 do not survive to the adult stage (PubMed:24700158). Double bocks and Ote mutants larvae have small brains, their imaginal disks are reduced in size or absent, and only 10% of second-instar larvae reach the pupal stage (PubMed:24700158). In bocks and MAN1 double mutants, pupal survival and larvae development is unaffected (PubMed:24700158).