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Background
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Prelamin A is the precursor of mature lamin A, a structural protein of the nuclear lamina and it is encoded by LMNA gene. Prelamin A carrying the R527H mutation is found in subjects affected by Mandibuloacral Dysplasia type A [MADA, OMIM no. 248370]. MADA is a rare and complex disease characterized by postnatal growth retardation, craniofacial anomalies, skeletal malformations, mottled cutaneous pigmentation, partial lipodystrophy (type A pattern), and insulin resistance. MADA patients seem to be genetically homogeneous, since they show the same mutation (R527H) in the LMNA gene. In contrast, patients with generalized loss of subcutaneous fat involving the face, trunk, and extremities (type B pattern) carry mutations in the ZMPSTE24 gene (MADB, OMIM no. 608612). MADA is a specific genetic entity belonging to a class of genetic disorders called "laminopathies". The R527H lamin A/C mutation produces accumulation of unprocessed prelamin A, altered distribution of the lamin B receptor (LBR), and destabilization of two heterochromatin-associated proteins, histone H3 methylated at lysine 9 (Me9H3) and heterochromatin protein-1? (HP1?).
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