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Novel ALDH3A2 Heterozygous Mutations Are Associated with Defective Lamellar Granule Formation in a Japanese Family of Sjögren–Larsson Syndrome

2004; Elsevier BV; Volume: 123; Issue: 6 Linguagem: Inglês

10.1111/j.0022-202x.2004.23505.x

1523-1747

Akihiko Shibaki, Masashi Akiyama, Hiroshi Shimizu,

Plant Reproductive Biology

aldehyde dehydrogenase fatty aldehyde dehydrogenase Sjögren–Larsson syndrome To the Editor: Sjögren–Larsson syndrome (SLS: MIM# 270200) is an autosomal recessive disorder characterized by congenital ichthyosis, mental retardation, and spastic paresis (Rizzo, 1993Rizzo W.B. Sjögren–Larsson syndrome.Semin Dermatol. 1993; 2: 210-218Google Scholar).Rizzo et al., 1988Rizzo W.B. Dammann A.L. Craft D.A. Sjögren–Larsson syndrome. Impaired fatty alcohol oxidation in cultured fibroblasts due to deficient fatty alcohol: Nicotinamide adenine dinucleotide oxidoreductase activity.J Clin Invest. 1988; 81: 737-744Crossref Scopus (102) Google Scholar demonstrated that long-chain fatty alcohol was deposited in cultured fibroblasts, white blood cells, and serum in SLS patients. Later,De Laurenzi et al., 1996De Laurenzi V. Rogers G.R. Hamrock D.J. et al.Sjögren–Larsson syndrome is caused by mutations in the fatty aldehyde dehydrogenase gene.Nat Genet. 1996; 12: 52-57https://doi.org/10.1038/ng0196-52Crossref PubMed Scopus (229) Google Scholar reported that mutations in the fatty aldehyde dehydrogenase (FALDH) gene (ALDH3A2) were responsible for the development of SLS. However, the exact pathomechanisms of this ichthyosis in SLS is not fully understood. In this study, we report novel heterozygous mutations in ALDH3A2 in a Japanese family with SLS. In this family, a combination of heterozygous mutations is associated with defective lamellar granules and abnormal intercellular lipid in the stratum corneum. Case 1: A 6-year-old girl with congenital ichthyosis, mental retardation, and spastic paresis in both her lower extremities, visited our clinic (Figure 1a). Physical examination revealed xerosis and fine scales over her whole body, and lamellar-shaped scales on her dorsal hands and feet. Her lower extremities were hypertonic. Brain magnetic resonance imaging (MRI) demonstrated a high-intensity area in the postangular area of the left parietal lobe. Ophthalmologic examination was unremarkable. Case 2: A 1-year-old boy, the younger brother of case 1, was brought to our clinic suffering from congenital ichthyosis, mental retardation, and spastic paresis on both his lower extremities. Physical examination revealed brown-colored pigmentation with mild to moderate hyperkeratosis on his neck, with fine, dark scales on the dorsal feet (Figure 1b). No other abnormalities, including ophthalmologic problems, were observed. To elucidate the genetic abnormality of the patients, blood samples were collected from both patients and their parents. All the experiments, skin biopsies and blood sampling were performed with the parents' written informed consent and with the institutional approval of Hokkaido University Graduate School of Medicine for experiments handling human matter in accordance with Helsinki Principles. The ALDH3A2 gene was amplified by the methods previously reported byRizzo et al., 1999Rizzo W.B. Carney G. Lin Z. The molecular basis of Sjögren–Larsson syndrome: Mutation analysis of the fatty aldehyde dehydrogenase gene.Am J Hum Genet. 1999; 65: 1547-1560https://doi.org/10.1086/302681Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar. DNA sequencing of all the PCR products was carried out using a Genetic Analyzer 310A automatic sequencer (Perkin-Elmer Life Sciences-ABI, Foster City, California). In both children, we detected a combination of heterozygous mutations in exon 4 and 7 (Figure 1c). The mutation in exon 4 (481delA) was only present in their mother, and the mutation in exon 7 (1087–1089delGTA) was only demonstrated in their father. The presence of both these mutations was excluded in 100 alleles of 50 normal unrelated Japanese individuals. Histopathological examination of the skin biopsy specimens obtained from both cases revealed orthohyperkeratosis with mild hypergranulosis (Figure 2a). Electron microscopic examination of osmium tetroxide-fixed samples from the lesional skin of both patients, demonstrated the abnormal lamellar granules lacking the normal lamellar contents (Figure 2b). Some of the defective lamellar granules secreted their components into the intercellular space in the stratum corneum. Irregularly shaped granular and electron-lucent materials were also deposited in the dilated intercellular space between corneocytes (Figure 2c–e). Variously sized empty vacuoles, presumably containing electron lucent lipid, were also seen in the stratum corneum (Figure 2b,c). Immunofluorescent staining for keratin 1, 10, loricrin, and involucrin, performed as described previously (Akiyama et al., 1998Akiyama M. Christiano A.M. Yoneda K. Shimizu H. Abnormal cornified cell envelope formation in mutilating palmoplantar keratoderma unrelated to epidermal differentiation complex.J Invest Dermatol. 1998; 111: 133-138https://doi.org/10.1046/j.1523-1747.1998.00230.xCrossref PubMed Scopus (15) Google Scholar), revealed that all of these molecules were normally distributed in the epidermis (data not shown). The distribution pattern of a trans-Golgi network marker, TGN-46 and a lamellar granule component, cathepsin D (Ishida-Yamamoto et al., 2004Ishida-Yamamoto A. Simon M. Kishibe M. et al.Epidermal lamellar granules transport different cargoes as distinct aggregates.J Invest Dermatol. 2004; 122: 1137-1144https://doi.org/10.1111/j.0022-202X.2004.22515.xAbstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar) were normal, although immunofluorescent staining for glucosylceramides revealed an abnormal, irregular or granular distribution of glucosylceramides in the patients' stratum corneum (data not shown). Normal epidermal transglutaminase activity was confirmed in both patients by the insitu transglutaminase activity assays previously described elsewhere (Hohl et al., 1998Hohl D. Aeschlimann D. Huber M. In vitro and rapid insitu transglutaminase assays for congenital ichthyoses—a comparative study.J Invest Dermatol. 1998; 110: 261-268https://doi.org/10.1046/j.1523-1747.1998.00132.xCrossref Scopus (49) Google Scholar;Raghunath et al., 1998Raghunath M. Hennies H.C. Velten F. Wiebe V. Steinert P.M. Reis A. Traupe H. A novel insitu method for the detection of deficient transglutaminase activity in the skin.Arch Dermatol Res. 1998; 290: 621-627https://doi.org/10.1007/s004030050362Crossref PubMed Scopus (60) Google Scholar;Akiyama et al., 2001Akiyama M. Takizawa Y. Suzuki Y. Ishiko A. Matsuo I. Shimizu H. Compound heterozygous TGM1 mutations including a novel missense mutation L204Q in a mild form of lamellar ichthyosis.J Invest Dermatol. 2001; 116: 992-995https://doi.org/10.1046/j.0022-202x.2001.01367.xCrossref PubMed Google Scholar) (data not shown). FALDH is a microsomal NAD-dependent enzyme, which is necessary for the oxidation of long-chain aliphatic aldehydes to fatty acids (Kelson et al., 1997Kelson T.L. Secor McVoy J.R. Rizzo W.B. Human liver fatty aldehyde dehydrogenase: Microsomal localization, purification, and biochemical characterization.Biochim Biophys Acta. 1997; 1335: 99-110Crossref PubMed Scopus (117) Google Scholar). Until now, several mutations in ALDH3A2 have been shown to be responsible for SLS around the world (Rizzo et al., 1999Rizzo W.B. Carney G. Lin Z. The molecular basis of Sjögren–Larsson syndrome: Mutation analysis of the fatty aldehyde dehydrogenase gene.Am J Hum Genet. 1999; 65: 1547-1560https://doi.org/10.1086/302681Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar). In our cases, a heterozygous combination of two novel mutations has been identified. The maternal mutation 481delA in exon 4 resulted in a frame-shift leading to a stop codon at codon 522. This premature translation termination eliminates the downstream 64% of ALDH3A2 coding sequences. The paternal mutation 1087–1089delGTA in exon 7 resulted in a deletion of valine at position 363 of FALDH protein. According to a comparison of 145 full-length ALDH-related sequences byPerozich et al., 1999Perozich J. Nicholas H. Wang B.-C. Lindahl R. Hempel J. Relationships within the aldehyde dehydrogenase extended family.Protein Sci. 1999; 8: 137-146Crossref PubMed Scopus (248) Google Scholar, this valine is highly conserved among many of the ALDH family members, and participates in one of the ten most conserved sequence motifs in ALDH. In addition, analysis of the crystallized 3-D structure of the related class 3 rat cytosolic ALDH revealed that this valine is located at one of the six parallels of β-strands, β11, comprising the catalytic domain of the molecule (Figure 1d) (Liu et al., 1997Liu Z.-J. Sun Y.-J. Rose J. et al.The first structure of an aldehyde dehydrogenase reveals novel interactions between NAD and the Rossmann fold.Nat Struct Biol. 1997; 4: 317-326https://doi.org/10.1038/nsb0497-317Crossref PubMed Scopus (276) Google Scholar). These findings strongly suggest that valine at position 363 is important for structural folding of the catalytic domain and are therefore essential for the normal function of the FALDH protein. Previously, abnormal lamellar or membranous inclusions in the cornified cells were observed in the lesional skin of a SLS patient, although causative genetic abnormalities were not known in that particular case (Ito et al., 1991Ito M. Oguro K. Sato Y. Ultrastructural study of the skin in Sjögren–Larsson syndrome.Arch Dermatol Res. 1991; 283: 141-148https://doi.org/10.1007/BF00372053Crossref PubMed Scopus (32) Google Scholar). The inclusions were speculated to be lamellar granule-in-origin. Later, a deficiency in acyl-ceramides in the lipid layer in the stratum corneum was also reported in SLS patients (Paige et al., 1994Paige D.G. Morse-Fisher N. Harper J.I. Quantification of stratum corneum ceramides and lipid envelope ceramides in the hereditary ichthyoses.Br J Dermatol. 1994; 131: 23-27Crossref PubMed Scopus (94) Google Scholar). In addition to these previous observations, we revealed that the malformed lamellar granule components were secreted into the intercellular space, and irregular-shaped granular and electron-lucent materials were deposited in the irregularly dilated intercellular space in stratum corneum. Immunofluorescence studies revealed an abnormal distribution of glycosylceramide, a lamellar granule component, in the patients' stratum corneum. These observations together suggest defective lamellar granule formation in these patients. Similarly, a large number of abnormal lamellar granules associated with disturbed intercellular lamellar structures were observed in ichthyotic skin in a patient with Dorfman–Chanarin syndrome (Akiyama et al., 2003Akiyama M. Sawamura D. Nomura Y. Sugawara M. Shimizu H. Truncation of CGI-58 protein causes malformation of lamellar granules resulting in ichthyosis in Dorfman–Chanarin syndrome.J Invest Dermatol. 2003; 121: 1029-1034https://doi.org/10.1046/j.1523-1747.2003.12520.xAbstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar). Furthermore, in harlequin ichthyosis, lamellar granules are completely absent or, if present, are not correctly secreted into the intercellular space (Milner et al., 1992Milner M.E. O'Guin W.M. Holbrook K.A. Dale B.A. Abnormal lamellar granules in harlequin ichthyosis.J Invest Dermatol. 1992; 99: 824-829https://doi.org/10.1111/1523-1747.ep12614791Abstract Full Text PDF PubMed Scopus (86) Google Scholar). Thus, the present ultrastructural and immunofluorescence findings suggest that formation of defective lamellar granule contents and defective intercellular lipids, presumably related to the mutations in ALDH3A2, may lead to the ichthyotic skin developed in SLS patients. This work was supported in part by a grant-in-aid from the Ministry of Education, Culture, Sports, Science and Technology (B16390312 to M. A.).