BRUCE is a highly conserved 528-kDa peripheral membrane protein of the trans-Golgi network. Owing to the presence of an N-terminal single baculovirus inhibitor repeat, BRUCE functions as an inhibitor of apoptosis protein and blocks apoptosis when overexpressed. In addition, due to the presence of a C-terminal ubiquitin-conjugating domain, BRUCE can covalently attach ubiquitin to substrates. Here we report the generation and characterization of BRUCE-deficient mice. Complete inactivation of the BRUCE gene resulted in perinatal lethality and growth retardation discernible after embryonic day 14. The growth defect is linked to impaired placental development and may be caused by insufficient oxygen and nutrient transfer across the placenta. Chorioallantoic placentation initiated normally, but the mutant placenta showed an impaired maturation of the labyrinth layer and a significant reduction of the spongiotrophoblast. No evidence for an elevated apoptosis rate was detectable in embryonic and extraembryonic tissues and in knockout fibroblasts. Thus, although BRUCE is broadly expressed in embryonic, extraembryonic, and adult mouse tissues, this bifunctional protein might play a unique role in normal trophoblast differentiation and embryonic survival.

Previous studies on the development of cleft lip, alveolus, palate, and velum and neural tube defects have revealed several shared multifactorial causes. Both anomalies emerge at different times during embryonic development and are not associated with each other unless there is a genetic component to the etiology. Vitamin deficiency disorders are one of several factors contributing to the etiology of these anomalies.Vitamins B6, folic acid and B12 play an essential role in the methylation cycle. A lack of or deficiency in these vitamins thus has severe consequences for the organism, especially the unborn child. Due to its short half-life, vitamin B6 is particularly important for undisturbed embryogenesis and should be taken along with folic acid as a periconceptional supplement to prevent embryonic deformities. This paper is intended to provide the orthodontist (as a member of the interdisciplinary cleft team) with an overview of the issues and etiological significance of vitamin B deficiencies as possible inducers of these embryopathies. This may encourage comprehensive counselling, particularly of parents of children born with deformities who wish to have more children.

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