Further, CNN showed a weak but significant direct inhibitory effect on the enzymatic activity of tyrosinase, suggesting one possible mechanism of hypopigmentation.
Tyrosinase catalyzes the key step of melanogenesis, dysfunction of tyrosinase leads to reduce melanin production which results in severe clinical and aesthetical problems of hypopigmentation.
Taken together, CFAB is a unique reagent that primarily accelerates tyrosinase decrease by a mechanism that differs from those considered for other hypopigmentation reagents currently reported.
The substantial reduction of SLC45A2 protein in the patient's melanocytes caused the mislocalization of tyrosinase from melanosomes to the plasma membrane and also led to the incorporation of tyrosinase into exosomes and secretion into the culture medium, explaining the hypopigmentation in OCA-4.
Yellow oculocutaneous albinism (OCA) that is caused by tyrosinase gene mutations shows two characteristics: extreme hypopigmentation at birth and the eventual development of yellow or blond hair.
Tyrosinase inhibition due to interaction of homocyst(e)ine with copper: the mechanism for reversible hypopigmentation in homocystinuria due to cystathionine beta-synthase deficiency.
A novel type I OCA phenotype in which hypopigmentation is related to local body temperature is associated with a missense substitution in tyrosinase, codon 422 CGG (Arg)----CAG (Gln).
Hairbulb tyrosinase activity and glutathione content, as well as urine cysteinyldopa excretion, were low in PWS individuals with and without hypopigmentation and did not separate these two groups.
Importantly, our data imply that the same SOX10 mutations can underlie both typical WS and KS with deafness without skin/hair hypopigmentation, Hirschsprung disease, or neurological defects.
We identified a de novo nonsense mutation in SOX10 (p.G39X) in a female pediatric patient with Waardenburg syndrome with heterochromia iridis, profound bilateral sensorineural hearing loss, inner ear malformations, and overall hypopigmentation of the hair without dystopia canthorum.
Interestingly, the WS4 family carries an insertion of 19 nucleotides in exon 5 of SOX10, which results in distinct phenotypes along three different generations: hypopigmentation in the maternal grandmother, hearing loss in the mother, and WS4 in the proband.
Complementation tests using a second allele of Gli3 (Gli3(Xt-J)) confirmed that a null mutation of Gli3 causes the increased hypopigmentation in Sox10(LacZ/+);Gli3(Mos1/)(+) double heterozygotes.
The neural crest disorders in the Sox10(Dom) mice and WS-IV patients consist of hypopigmentation, cochlear neurosensory deafness, and enteric aganglionosis.
Griscelli syndrome type 2 (GS2) is a rare autosomal-recessive disorder associated with a RAB27A gene mutation, and clinically manifesting as hypopigmentation, disseminated chronic encephalitis, and severe immunological disorders characterized by an accelerated hematological phase, also referred to as hemophagocytic syndrome (HS), or hemophagocytic lymphohistiocytosis (HLH).
Griscelli syndrome type 2 is a rare autosomal recessive primary immunodeficiency disease caused by a mutation in the RAB27A gene and characterized by oculocutaneous hypopigmentation and variable cellular immunodeficiency.
Griscelli syndrome (GS) is caused by mutations in the MYO5A (GS1), RAB27A (GS2), or MLPH (GS3) genes, all of which lead to a similar pigmentary dilution.
Rab27a plays a pivotal role in the transport of melanosomes to dendrite tips of melanocytes and mutations in RAB27A, which impair melanosome transport cause the pigmentary dilution and the immune deficiency found in several patients with Griscelli syndrome (GS).
Besides hypopigmentation and bilateral HL, the homozygous mutant pig (MITF <sup>L247S/L247S</sup>) and CRISPR/Cas9-mediated MITF bi-allelic knockout pigs both exhibited anophthalmia.
Mutations in the MITF have been found in patients with the dominantly inherited hypopigmentation and deafness syndromes Waardenburg syndrome type 2A (WS2A) and Tietz syndrome (TS).
Besides neurological deficit, hypopigmentation is another phenotype associated with AS patients currently attributed to the hemizygosity of the type II oculocutaneous albinism (OCA2) gene.