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Palmoplantar keratoderma along with neuromuscular and metabolic phenotypes in Slurp1-deficient mice.

Adeyo O, Allan BB, Barnes RH, Goulbourne CN, Tatar A, Tu Y, Young LC, Weinstein MM, Tontonoz P, Fong LG, Beigneux AP, Young SG - J. Invest. Dermatol. (2014)

Bottom Line: SLURP1 is a secreted protein that is expressed highly in keratinocytes but has also been identified elsewhere (e.g., spinal cord neurons).In addition, Slurp1(-/-) mice exhibited reduced adiposity, protection from obesity on a high-fat diet, low plasma lipid levels, and a neuromuscular abnormality (hind-limb clasping).Initially, it was unclear whether the metabolic and neuromuscular phenotypes were due to Slurp1 deficiency, because we found that the targeted Slurp1 mutation reduced the expression of several neighboring genes (e.g., Slurp2, Lypd2).

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA.

ABSTRACT
Mutations in SLURP1 cause mal de Meleda, a rare palmoplantar keratoderma (PPK). SLURP1 is a secreted protein that is expressed highly in keratinocytes but has also been identified elsewhere (e.g., spinal cord neurons). Here, we examined Slurp1-deficient mice (Slurp1(-/-)) created by replacing exon 2 with β-gal and neo cassettes. Slurp1(-/-) mice developed severe PPK characterized by increased keratinocyte proliferation, an accumulation of lipid droplets in the stratum corneum, and a water barrier defect. In addition, Slurp1(-/-) mice exhibited reduced adiposity, protection from obesity on a high-fat diet, low plasma lipid levels, and a neuromuscular abnormality (hind-limb clasping). Initially, it was unclear whether the metabolic and neuromuscular phenotypes were due to Slurp1 deficiency, because we found that the targeted Slurp1 mutation reduced the expression of several neighboring genes (e.g., Slurp2, Lypd2). We therefore created a new line of knockout mice (Slurp1X(-/-) mice) with a simple nonsense mutation in exon 2. The Slurp1X mutation did not reduce the expression of adjacent genes, but Slurp1X(-/-) mice exhibited all of the phenotypes observed in the original line of knockout mice. Thus, Slurp1 deficiency in mice elicits metabolic and neuromuscular abnormalities in addition to PPK.

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Palmoplantar keratoderma and increased stratum corneum lipid droplets in Slurp1−/− mice(A) Paws from wild-type and Slurp1−/− mice, revealing markedly thickened skin in Slurp1−/− mice. (B–C) Hematoxylin and eosin–stained sections revealing a thickened epidermis in the paw skin of a Slurp1−/− mouse, along with many tiny lipid droplets in the stratum corneum (arrowheads). Scale bars = 50 µm and 10 µm for B and C respectively. (D) BODIPY 493/503 (green) staining showing lipid droplets in the stratum corneum (SC) of the paw skin of a Slurp1−/− mouse. DNA is stained with DAPI (blue). Scale bar = 50 µm. (E) Electron micrograph showing lipid droplets in the stratum corneum of Slurp1−/− paw skin (arrowheads). Scale bar = 1 µm. (F) Increased BrdU incorporation into DNA of paw keratinocytes of Slurp1−/− mice (green). DNA is stained with DAPI (red). Scale bar = 50 µm.
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Figure 1: Palmoplantar keratoderma and increased stratum corneum lipid droplets in Slurp1−/− mice(A) Paws from wild-type and Slurp1−/− mice, revealing markedly thickened skin in Slurp1−/− mice. (B–C) Hematoxylin and eosin–stained sections revealing a thickened epidermis in the paw skin of a Slurp1−/− mouse, along with many tiny lipid droplets in the stratum corneum (arrowheads). Scale bars = 50 µm and 10 µm for B and C respectively. (D) BODIPY 493/503 (green) staining showing lipid droplets in the stratum corneum (SC) of the paw skin of a Slurp1−/− mouse. DNA is stained with DAPI (blue). Scale bar = 50 µm. (E) Electron micrograph showing lipid droplets in the stratum corneum of Slurp1−/− paw skin (arrowheads). Scale bar = 1 µm. (F) Increased BrdU incorporation into DNA of paw keratinocytes of Slurp1−/− mice (green). DNA is stained with DAPI (red). Scale bar = 50 µm.

Mentions: Slurp1 knockout mice, created by replacing exon 2 with neo and lacZ cassettes (Fig. S1), appeared normal at birth but developed PPK by 6 weeks of age (Fig. 1 A–C). By H&E staining, the epidermis in Slurp1−/− paw skin was thickened and the stratum granulosum was poorly demarcated (Fig. 1 B). No inflammatory infiltrates were present. The stratum corneum contained abundant lipid droplets, as judged by H&E staining, BODIPY staining, and electron microscopy (Fig. 1 C–E). Lamellar bodies were present in stratum granulosum keratinocytes in both wild-type and Slurp1−/− mice, as determined by electron microscopy (Fig. S 2), but whether this technique is capable of picking up subtle differences in the efficiency of lamellar body secretion is uncertain. BrdU incorporation into keratinocytes of paw skin in Slurp1−/− mice was markedly increased (Fig. 1 F). Aside from the paw, the skin and hair of Slurp1−/− mice were normal, both grossly and by routine histology (Fig. S3). The gastrointestinal tract, bronchial epithelium, and lungs of Slurp1−/− mice were histologically normal. Humans with mal de Meleda have been reported to have perivascular lymphocytic infiltrates and perioral involvment (Bouadjar et al., 2000; Nath et al., 2012), but these features were not present in Slurp1−/− mice. Slurp1+/− mice were indistinguishable from wild-type mice.


Palmoplantar keratoderma along with neuromuscular and metabolic phenotypes in Slurp1-deficient mice.

Adeyo O, Allan BB, Barnes RH, Goulbourne CN, Tatar A, Tu Y, Young LC, Weinstein MM, Tontonoz P, Fong LG, Beigneux AP, Young SG - J. Invest. Dermatol. (2014)

Palmoplantar keratoderma and increased stratum corneum lipid droplets in Slurp1−/− mice(A) Paws from wild-type and Slurp1−/− mice, revealing markedly thickened skin in Slurp1−/− mice. (B–C) Hematoxylin and eosin–stained sections revealing a thickened epidermis in the paw skin of a Slurp1−/− mouse, along with many tiny lipid droplets in the stratum corneum (arrowheads). Scale bars = 50 µm and 10 µm for B and C respectively. (D) BODIPY 493/503 (green) staining showing lipid droplets in the stratum corneum (SC) of the paw skin of a Slurp1−/− mouse. DNA is stained with DAPI (blue). Scale bar = 50 µm. (E) Electron micrograph showing lipid droplets in the stratum corneum of Slurp1−/− paw skin (arrowheads). Scale bar = 1 µm. (F) Increased BrdU incorporation into DNA of paw keratinocytes of Slurp1−/− mice (green). DNA is stained with DAPI (red). Scale bar = 50 µm.
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Figure 1: Palmoplantar keratoderma and increased stratum corneum lipid droplets in Slurp1−/− mice(A) Paws from wild-type and Slurp1−/− mice, revealing markedly thickened skin in Slurp1−/− mice. (B–C) Hematoxylin and eosin–stained sections revealing a thickened epidermis in the paw skin of a Slurp1−/− mouse, along with many tiny lipid droplets in the stratum corneum (arrowheads). Scale bars = 50 µm and 10 µm for B and C respectively. (D) BODIPY 493/503 (green) staining showing lipid droplets in the stratum corneum (SC) of the paw skin of a Slurp1−/− mouse. DNA is stained with DAPI (blue). Scale bar = 50 µm. (E) Electron micrograph showing lipid droplets in the stratum corneum of Slurp1−/− paw skin (arrowheads). Scale bar = 1 µm. (F) Increased BrdU incorporation into DNA of paw keratinocytes of Slurp1−/− mice (green). DNA is stained with DAPI (red). Scale bar = 50 µm.
Mentions: Slurp1 knockout mice, created by replacing exon 2 with neo and lacZ cassettes (Fig. S1), appeared normal at birth but developed PPK by 6 weeks of age (Fig. 1 A–C). By H&E staining, the epidermis in Slurp1−/− paw skin was thickened and the stratum granulosum was poorly demarcated (Fig. 1 B). No inflammatory infiltrates were present. The stratum corneum contained abundant lipid droplets, as judged by H&E staining, BODIPY staining, and electron microscopy (Fig. 1 C–E). Lamellar bodies were present in stratum granulosum keratinocytes in both wild-type and Slurp1−/− mice, as determined by electron microscopy (Fig. S 2), but whether this technique is capable of picking up subtle differences in the efficiency of lamellar body secretion is uncertain. BrdU incorporation into keratinocytes of paw skin in Slurp1−/− mice was markedly increased (Fig. 1 F). Aside from the paw, the skin and hair of Slurp1−/− mice were normal, both grossly and by routine histology (Fig. S3). The gastrointestinal tract, bronchial epithelium, and lungs of Slurp1−/− mice were histologically normal. Humans with mal de Meleda have been reported to have perivascular lymphocytic infiltrates and perioral involvment (Bouadjar et al., 2000; Nath et al., 2012), but these features were not present in Slurp1−/− mice. Slurp1+/− mice were indistinguishable from wild-type mice.

Bottom Line: SLURP1 is a secreted protein that is expressed highly in keratinocytes but has also been identified elsewhere (e.g., spinal cord neurons).In addition, Slurp1(-/-) mice exhibited reduced adiposity, protection from obesity on a high-fat diet, low plasma lipid levels, and a neuromuscular abnormality (hind-limb clasping).Initially, it was unclear whether the metabolic and neuromuscular phenotypes were due to Slurp1 deficiency, because we found that the targeted Slurp1 mutation reduced the expression of several neighboring genes (e.g., Slurp2, Lypd2).

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA.

ABSTRACT
Mutations in SLURP1 cause mal de Meleda, a rare palmoplantar keratoderma (PPK). SLURP1 is a secreted protein that is expressed highly in keratinocytes but has also been identified elsewhere (e.g., spinal cord neurons). Here, we examined Slurp1-deficient mice (Slurp1(-/-)) created by replacing exon 2 with β-gal and neo cassettes. Slurp1(-/-) mice developed severe PPK characterized by increased keratinocyte proliferation, an accumulation of lipid droplets in the stratum corneum, and a water barrier defect. In addition, Slurp1(-/-) mice exhibited reduced adiposity, protection from obesity on a high-fat diet, low plasma lipid levels, and a neuromuscular abnormality (hind-limb clasping). Initially, it was unclear whether the metabolic and neuromuscular phenotypes were due to Slurp1 deficiency, because we found that the targeted Slurp1 mutation reduced the expression of several neighboring genes (e.g., Slurp2, Lypd2). We therefore created a new line of knockout mice (Slurp1X(-/-) mice) with a simple nonsense mutation in exon 2. The Slurp1X mutation did not reduce the expression of adjacent genes, but Slurp1X(-/-) mice exhibited all of the phenotypes observed in the original line of knockout mice. Thus, Slurp1 deficiency in mice elicits metabolic and neuromuscular abnormalities in addition to PPK.

Show MeSH
Related in: MedlinePlus