Severe mandibuloacral dysplasia-associated lipodystrophy and progeria in a young girl with a novel homozygous Arg527Cys LMNA mutation

Abstract

Context: Mandibuloacral dysplasia (MAD) is a rare autosomal recessive progeroid syndrome due to mutations in genes encoding nuclear lamina proteins, lamins A/C (LMNA) or prelamin A processing enzyme, and zinc metalloproteinase (ZMPSTE24).

Objective: The aim of the study was to investigate the underlying genetic and molecular basis of the phenotype of a 7-yr-old girl with MAD belonging to a consanguineous pedigree and with severe progeroid features and lipodystrophy.

Design and patient: The patient developed mandibular hypoplasia during infancy and joint stiffness, skin thinning, and mottled hyperpigmentation at 15 months. Progressive clavicular hypoplasia, acroosteolysis, and severe loss of hair from the temporal and occipital areas were noticed at 3 yr. At 5 yr, cranial sutures were still open and lipodystrophy of the limbs was prominent. GH therapy from the ages of 3-7 yr did not improve the short stature. Severe joint contractures resulted in abnormal posture and decreased mobility. We studied her skin fibroblasts for nuclear morphology and immunoblotting and determined the in vitro effects of various pharmacological interventions on fibroblasts.

Results: LMNA gene sequencing revealed a homozygous missense mutation, c.1579C>T, p.Arg527Cys. Immunoblotting of skin fibroblast lysate with lamin A/C antibody revealed no prelamin A accumulation. Immunofluorescence staining of the nuclei for lamin A/C in fibroblasts revealed marked nuclear morphological abnormalities. This abnormal phenotype could not be rescued with inhibitors of farnesyl transferase, geranylgeranyl transferase, or histone deacetylase.

Conclusion: Severe progeroid features in MAD could result from LMNA mutation, which does not lead to accumulation of prenylated lamin A or prelamin A.

Figure 1

MAD pedigree, LMNA mutation, and immunoblot from the patient’s fibroblasts. A, Pedigree of the MAD family. The proband with homozygous Arg527Cys LMNA mutation is shown as filled symbol, and the parents, heterozygous for the Arg527Cys mutation, are shown as half-filled symbols. Square symbols indicate males, and circles indicate females. Double horizontal lines indicate consanguinity. B, Sequence electropherogram for mutation in exon 9 of LMNA. Identified mutation c.1579C>T is marked by an arrow, and wild-type sequence is shown below for comparison. C, Immunoblot analysis of cell lysates. Shown is a representative immunoblot of cell lysates obtained from the fibroblasts of the affected patient (MAD 2200.3) probed with amino-terminal-specific antilamin A/C antibody, N-18, showing lamin C and mature lamin A. In the affected patient, no prelamin A was identified. Patient MAD 3300.3 with ZMPSTE24 deficiency and AG06917 with HGPS (with LMNA G608G heterozygous mutation) were included as positive controls to show prelamin A and progerin band, respectively. Normal control subject showed lamins A and C band as well.

Figure 2

Photographs of the patient at the age of 5 yr and growth chart. A, Frontal view of the total body; B, posterior view of the body; C, anterior view of the lower part of face; D, posterior view of the left hand; and E, anterior view of the abdomen. Note the characteristic faces, marked loss of scalp hair from the frontal and occipital region, mandibular hypoplasia, severe crowding of the maxillary and mandibular teeth, prominent vasculature on the tip of the nose with beaking of the nose, lipodystrophy (especially the loss of sc fat from the gluteal region), skin atrophy with mottled hyperpigmentation over the abdomen, drooping shoulders due to clavicular hypoplasia, contractures of the proximal and distal interphalangeal joints with marked acroosteolysis and finger tip rounding. F, Growth chart reveals her weight to be below the 95th percentile but an increase in linear growth with GH therapy after 3 yr of age (initial height indicated by the symbol X).

Figure 3

Skinfold thickness at various anatomic sites of our patient. Data from our patient are shown as filled circles. The shaded bars represent the median, 10th and 90th percentile values of skinfold thickness for normal 4- to 10-yr-old girls. [The data were collected on 106 females. The mean body mass index was 19.1 kg/m² (range, 12.8 to 34 kg/m²). There were 49 White girls from Vermont and 19 White and 38 Black girls from Alabama (27). Courtesy of M. I. Goran.] Clearly, her thigh, calf, triceps, suprailiac, and subscapular skinfold thickness was well below the 10th percentile of normal girls, suggestive of partial lipodystrophy.

Figure 4

Nuclear morphology of skin fibroblasts and response to various pharmacological agents. Indirect immunofluorescence microscopy using lamin A/C antibody (H-110) in fibroblasts obtained from a control subject and the patient, MAD 2200.3. A and B, Control cells in culture medium without and with dimethylsulfoxide (DMSO). C—F, Morphology after incubation of the cells for 48 h with 10 μm FTI-277 or FTI-III, GGT-297, or a histone deacetylase inhibitor, TSA, respectively. G and H, Fibroblasts from patient MAD 2200.3 showed misshapen nuclei with bilobed nuclei or nuclear blebs. These nuclear abnormalities did not affect the localization of lamin A to the periphery of the nucleus. I—L, Incubation of the cells with FTI-277, FTI-III, GGT-297 or TSA, respectively, did not correct these nuclear abnormalities. Note the aggregation of lamin A/C in the fibroblast nuclei from both the control and the patient incubated with FTIs (panels C, I).