The correct answer is B. Promotes aggregation and disulfide bonding of keratin filaments in a calcium-dependent process.

The case describes atopic dermatitis, which is associated with mutation in filaggrin. Filaggrin stands for filament aggregating protein. It is a major structural protein in the stratum corneum. Filaggrin is produced as the precursor, profilaggrin, which consists of multiple repeats of filaggrin. Profilaggrin is dephosphorylated and cleaved into functional filaggrin monomers. It is thought that filaggrin monomers aggregate and align keratin bundles in the cornified cell envelope which contributes to the strength and integrity of the stratum corneum. Breakdown products of filaggrin combined with sodium, chloride, lactate, and urea combine to form a natural moisturizing barrier, creating a skin barrier and allowing for epidermal hydration.

Desmosomal cadherins initiate and maintain intercellular adhesion of keratinocytes and epithelial cells. Antibodies to desmoglein 3 (+/- Dsg 1) are seen in pemphigus vulgaris. Desmoglein 1 is defective in striate Palmoplantar keratoderma. Cross-linking of structural proteins of the cornified envelope in a calcium-dependent process is performed by transglutaminase 3. Linkage between intermediate filaments of the extracellular matrix and basement membrane is performed by integrins. Regulating the cutaneous barrier and water-holding ability is performed by ceramides.

References:

Maeve A. McAleer, Alan D. Irvine, The multifunctional role of filaggrin in allergic skin disease, Journal of Allergy and Clinical Immunology, Volume 131, Issue 2, 2013, Pages 280-291, ISSN 0091-6749, https://doi.org/10.1016/j.jaci.2012.12.668.
Irit Gottfried, Marina Landau, Fabian Glaser, Wei-Li Di, Joseph Ophir, Barukh Mevorah, Nir Ben-Tal, David P. Kelsell, Karen B. Avraham, A mutation in GJB3 is associated with recessive erythrokeratodermia variabilis (EKV) and leads to defective trafficking of the connexin 31 protein, Human Molecular Genetics, Volume 11, Issue 11, 2002, Pages 1311–1316, https://doi.org/10.1093/hmg/11.11.1311
Harding, Clive R. “The stratum corneum: structure and function in health and disease.” Dermatologic therapy 17 (2004): 6-15.
Samuelov, L., Sarig, O., Harmon, R. et al. Desmoglein 1 deficiency results in severe dermatitis, multiple allergies and metabolic wasting. Nat Genet 45, 1244–1248 (2013). https://doi.org/10.1038/ng.2739
Jouni Uitto, Gabriele Richard, John A. McGrath, Diseases of epidermal keratins and their linker proteins, Experimental Cell Research, Volume 313, Issue 10, 2007, Pages 1995-2009,
ISSN 0014-4827, https://doi.org/10.1016/j.yexcr.2007.03.029.

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