Hirobe Tomohisa, Abe Hiroyuki
Radiation Effect Mechanism Research Group, National Institute of Radiological Sciences, Anagawa, Inage-ku, Chiba, Japan.
Anat Rec (Hoboken). 2007 Aug;290(8):981-93. doi: 10.1002/ar.20547.
The slaty (Dct(slt)) mutation is known to reduce the activity of dopachrome tautomerase, which converts dopachrome to 5,6-dihydroxyindole-2-carboxylic acid in the pathway of eumelanin synthesis and to inhibit melanosome maturation in melanocytes. However, it is not known whether the inhibition of melanosome maturation in slaty melanocytes is developmentally regulated. To address this point, changes in the morphology and maturation of melanosomes in cultured epidermal melanocytes derived from newborn mice of wild-type (black) and slaty mutant were surveyed under the electron microscope. In black melanocytes (Dct(+)), almost all melanosomes were elliptical stage IV melanosomes. However, in slaty melanocytes, numerous spherical stage III melanosomes with globular depositions of pigment in addition to elliptical stage III melanosomes with intraluminal fibrils were observed. Mixed-type melanosomes containing both globular deposition and intraluminal fibrils of pigment were also observed. In slaty melanocytes, spherical and mixed-type melanosomes were gradually decreased after birth, whereas elliptical melanosomes were gradually increased. Stage IV melanosomes were very few in slaty melanocytes, and the number did not increase after birth. These results suggest that the slaty mutation blocks the melanosome maturation at stage III and affects the melanosome morphology (elliptical or spherical) in a developmental stage-specific manner.
已知石板色（Dct(slt)）突变会降低多巴色素互变异构酶的活性，该酶在真黑素合成途径中将多巴色素转化为5,6 - 二羟基吲哚 - 2 - 羧酸，并抑制黑素细胞中的黑素体成熟。然而，尚不清楚石板色黑素细胞中黑素体成熟的抑制是否受到发育调控。为了解决这一问题，在电子显微镜下观察了源自野生型（黑色）和石板色突变新生小鼠的培养表皮黑素细胞中黑素体的形态和成熟变化。在黑色黑素细胞（Dct(+)）中，几乎所有黑素体都是椭圆形的IV期黑素体。然而，在石板色黑素细胞中，除了具有腔内纤维的椭圆形III期黑素体之外，还观察到许多带有球状色素沉积的球形III期黑素体。还观察到含有球状色素沉积和腔内纤维的混合型黑素体。在石板色黑素细胞中，球形和混合型黑素体在出生后逐渐减少，而椭圆形黑素体逐渐增加。IV期黑素体在石板色黑素细胞中非常少，并且出生后数量没有增加。这些结果表明，石板色突变在III期阻断黑素体成熟，并以发育阶段特异性方式影响黑素体形态（椭圆形或球形）。
