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Basic Science
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
In 2008, Ginger et al. [9] observed downregulation of melanin production by inserting SLC24A5*Thr111 allele into DNA of cultured melanocytes. The following hypothesis was proposed: This mutation could change the pH of the trans-Golgi network, thereby modifying tyrosinase activity.Based on the timing of SLC24A5 expression during cell proliferation, it could also modulate the trafficking of pre-melanosomes.
Approach to hypopigmentation
Published in Electra Nicolaidou, Clio Dessinioti, Andreas D. Katsambas, Hypopigmentation, 2019
Clio Dessinioti, Andreas D. Katsambas
Cutaneous pigmentation is a complex human trait, influenced by melanin, capillary blood flow, cutaneous chromophores (lycopene, carotene), and collagen in the dermis. The synthesis and type of melanin and its distribution within melanosomes are genetically regulated by a number of genes, such as MC1R, TYR, OCA2, SLC24A5, MATP, and ASIP.1
The melanocyte and melaninogenesis
Published in Dimitris Rigopoulos, Alexander C. Katoulis, Hyperpigmentation, 2017
Dimitrios Xekardakis, Sabine Krueger-Krasagakis, Konstantinos Krasagakis
Several ion channels seem to have specific roles in melaninogenesis. These channels function at the plasma membrane and at the membrane of intracellular organelles of the melanocytes. The three most important ion channels that operate across the plasma membrane and modulate pigmentation are TRPM1, TRPM7, and TRPA1. They all belong to the transient receptor potential (TRP) channel family. TRPM1 levels are associated with basal pigmentation, according to the fact that a reduction of TRPM1 expression leads to decreased cellular melanin content. TRPM1 expression is controlled by MITF. On the other hand, TRPA1 is activated by ultraviolet A (UVA) and contributes to a rapid increase of melanin. The exact role of TRPM7 in melaninogenesis remains unknown. The most important intracellular ion channels are the endolysosomal TRPML channels, which belong to the mucolipin (ML) subfamily of TRP channels and regulate melanosomal function; the TPC (two-pore channels), which are expressed in acidic organelles and are regulators of melanosomal physiology and pigmentation; and the ClC-7 (chloride channels, isoform 7), which affect the melanosomal differentiation. There are also melanosomal-specific ion channel proteins that regulate at various steps the melaninogenesis that takes place in the melanosome. The most important of them are OCA2, SLC45A2, SLC24A5, and the OA1 ATPases.23 Finally, mitochondrial dynamics regulate melaninogenesis by accelerating degradation of MITF, via modulation of the signaling pathway reactive oxygen species (ROS)–ERK.24
The challenges faced by clinicians diagnosing and treating infantile nystagmus Part I: diagnosis
Published in Expert Review of Ophthalmology, 2021
Eleni Papageorgiou, Irene Gottlob
Albinism has been traditionally divided into oculocutaneous albinism (OCA) or ocular albinism (OA) on the basis of phenotypical features. However, the recent advances in molecular genetics have expanded the classification of various albinism subtypes based on the genetic profile of patients. Oculocutaneous albinism (OCA) is characterized by disruption of melanin biosynthesis, resulting in a lack of pigmentation in the eyes, skin, and hair [80]. Oculocutaneous albinism is a group of autosomal recessive disorders which are classified into seven types according to the affected gene [81]. OCA1 is caused by mutations in the tyrosinase gene (TYR) and is present in most populations except African-Americans [81]. It can present with either a complete lack of melanin production (OCA1A) or partial melanin production (OCA1B). Mutations in OCA2, TYRP1, SLC45A2, SLC24A5, and LRMDA have been attributed to subtypes OCA2, OCA3, OCA4, OCA6, and OCA7, respectively [81]. OCA2 and OCA3 are more common in African populations and are milder forms of albinism. OCA4 is another mild form of albinism that has been recently found in Turkish, Japanese, German, and Korean patients [81]. For OCA6 and OCA7 there are only case reports in a Chinese family and a consanguineous Faroese family. OCA5 is very rare, and has been only mentioned in a case report of a Pakistani family. The OCA5 locus is at 4q24, but the causative gene has not yet been identified [82].
How have our clocks evolved? Adaptive and demographic history of the out-of-African dispersal told by polymorphic loci in circadian genes
Published in Chronobiology International, 2018
Arcady A. Putilov, Vladimir B. Dorokhov, Michael G. Poluektov
The analyzed set of 1665 polymorphisms (Table 1, upper part) included single nucleotide polymorphisms (SNPs) and short indels (deletions and insertions) mapped in 12 reference genes (DBH, SLC6A3, DRD3, NPSR1, BDNF, CACNA1C, ACE, ACTN3, PPARA, GRIK3, TMEM132D and BRAF), 12 circadian genes (PER1, PER2, PER3, CLOCK, TIM, RORC, RORA, ARNTL, NPAS2, NFIL3, NR1D1 and CSNK1E) and 12 skin pigmentation genes (TMEM138, DDB1, TYRP1, MC1R, SLC24A5, SLC45A2, MFSD12, KITLG, TYR, OCA2, GRM5 and HERC2). Previously, the polymorphisms in the first three on the reference genes (DBH, SLC6A3 and DRD3) were associated with individual variation and alteration in dopaminergic neurotransmission (e.g., Corominas et al. 2009; Gray and MacKillop 2014; Mandelli and Serretti 2013; Paclt et al. 2004). Reliable evidence from several candidate gene studies (e.g., Bhat et al. 2012; Howe et al. 2016; Muglia et al. 2003; Schumacher et al. 2005) supported the associations of the polymorphic loci in the next three genes (NPSR1, BDNF and CACNA1C) with mental disorders. The polymorphic loci in ACE, ACTN3 and PPARA can be regarded as the three most replicable genetic markers of achievements in sport (e.g., reviewed by Ahmetov et al., 2015; Ahmetov et al. 2016). The last three reference genes (GRIK3, TMEM132D and BRAF) were shown to be involved in regulation of neurobehavioral functioning and, in particular, in the response to the processes of domestication of different animal species (e.g., dog and cattle) and to the process of self-domestication of anatomically modern humans (Erhardt et al. 2012; Hodgson et al. 2016; Minelli et al. 2009; Theofanopoulou et al. 2017). As for the structural genetic markers of variation in skin color, they were reliably identified in several genome-wide association studies in, at least, 12 genes (Beleza et al. 2013; Crawford et al. 2017; Jablonski and Chaplin 2013; Sturm 2009).
Mutation Analysis of 63 Northwest Chinese Probands with Oculocutaneous Albinism
Published in Current Eye Research, 2021
Zhang Chuan, Yousheng Yan, Shengju Hao, Qinghua Zhang, Bingbo Zhou, Xuan Feng, Xing Wang, Furong Liu, Lei Zheng, Zongfu Cao, Xu Ma
OCA is a heterogeneous and autosomal recessive disorder. OCA1, caused by mutations in the TYR gene, OCA2, OCA3, and OCA4 are somewhat milder forms of the disorder, caused by mutations in the OCA2, TYRP1, and MATP (SLC45A2) genes, respectively. OCA5 has been mapped to chromosome 4q24. Mutations of SLC24A5 gene caused OCA6, and OCA7 is caused by mutations in the C10ORF11 gene (http://www. omim.org/).