The Effects of a Mutant Connexin 26 on Epidermal Differentiation

Bakirtzis, George; Jamieson, Susan; Aasen, Trond; Bryson, Sheila; Forrow, Stephen; Tetley, Laurence; Finbow, Malcolm E.; Greenhalgh, David; Hodgins, Malcolm B.

doi:10.1080/cac.10.4-6.359.364

Cited by 22 publications

(21 citation statements)

References 23 publications

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“…The G59A mutation causes a less severe palmoplantar hyperkeratosis and sensorineural deafness (22). Preliminary studies by Di et al (17) showed that D66H was retained within an unidentified intracellular compartment when expressed in HeLa cells and intracellular retained D66H was also observed in suprabasal keratinocytes in D66H transgenic mice (53). During the preparation of this manuscript, Marziano et al (54) reported that D66H and G59A mutations were both retained in a perinuclear localization; furthermore D66H exerted a dominant-negative effect on Cx26 but not Cx30, whereas G59A had a dominantnegative effect on Cx30 but surprisingly not on wild-type Cx26 (54).…”

Section: Discussionmentioning

confidence: 99%

Functional Domain Mapping and Selective Trans-dominant Effects Exhibited by Cx26 Disease-causing Mutations

Thomas

Telford

Laird

2004

Journal of Biological Chemistry

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Mutations in Cx26 are a major cause of autosomal dominant and recessive forms of sensorineural deafness. Some mutations in Cx26 are associated not only with deafness but also with skin disease. We examined the subcellular localization and function of two green fluorescent protein (GFP)-tagged Cx26 point mutants that exhibit both phenotypes, G59A-GFP and D66H-GFP. D66H-GFP was retained within the brefeldin A-insensitive trans-Golgi network, whereas a population of G59A-GFP was transported to the cell surface. Neither G59A nor D66H formed gap junctions that were permeable to small fluorescent dyes, suggesting they are loss-of-function mutations. When co-expressed with wild-type Cx26, both G59A and D66H exerted dominant-negative effects on Cx26 function. G59A also exerted a trans-dominant negative effect on co-expressed wild type Cx32 and Cx43, whereas D66H exerted a trans-dominant negative effect on Cx43 but not Cx32. We propose that the severity of the skin disease is dependent on the specific nature of the Cx26 mutation and the trans-dominant selectivity of the Cx26 mutants on co-expressed connexins. Additional systematic mutations at residue D66, in which the overall charge of this motif was altered, suggested that the first extracellular loop is critical for Cx26 transport to the cell surface as well as function of the resulting gap junction channels.

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Section: Discussionmentioning

confidence: 99%

Functional Domain Mapping and Selective Trans-dominant Effects Exhibited by Cx26 Disease-causing Mutations

Thomas

Telford

Laird

2004

Journal of Biological Chemistry

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“…In this seminal study, the authors engineered a mouse that expressed the Cx26 D66H mutant driven by the keratin-10 promoter and that exhibited the mild to moderate sensorineural hearing loss and Vohwinkel syndrome (39). This mouse was viable and, notably, exhibited the hallmark keratoderma characteristics of patients that harbor this mutation and suffer from Vohwinkel syndrome.…”

Section: Mouse Models Of Connexin Diseasementioning

confidence: 99%

“…Although channel malformation is the most common feature of Cx26 and Cx43 mutants, a second class of mutants (e.g. Cx26 D66H (27) and Cx43 fs260 (25)) exhibit protein trafficking defects. In the case of the D66H mutant, it may still retain the capacity to reach the cell surface but fail to stabilize and return to the trans-Golgi network, where it is most prevalent (29).…”

Section: Expression Of Cx26 and Cx43 Mutants In Reference Cell Linesmentioning

confidence: 99%

“…Over half of the autosomal dominant Cx26 mutants (27)(28)(29) and ϳ10 Cx43 mutants (30 -33) have been assessed using this basic approach and found to exhibit two distinct subcellular localization profiles. First, the vast majority of mutants reach the cell surface and assemble into gap junction-like structures as assessed by light microscopy.…”

Section: Expression Of Cx26 and Cx43 Mutants In Reference Cell Linesmentioning

confidence: 99%

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Closing the Gap on Autosomal Dominant Connexin-26 and Connexin-43 Mutants Linked to Human Disease

Laird

2008

Journal of Biological Chemistry

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Cells within the vast majority of human tissues communicate directly through clustered arrays of intercellular channels called gap junctions. Gene ablation studies in mouse models have revealed that these intercellular channels are necessary for a variety of organ functions and that some of these genes are essential for survival. Molecular genetics has uncovered that germ line mutations in nearly half of the genes that encode the 21-member connexin family of gap junction proteins are linked to one or more human diseases. Frequently, these mutations are autosomal recessive, whereas in other cases, autosomal dominant mutations manifest as disease. Given the broad and overlapping distribution of connexins in a wide arrangement of tissues, it is hard to predict where connexin-linked diseases will clinically manifest. For instance, the most prevalent connexin in the human body is connexin-43 (Cx43), yet autosomal dominant mutations in the GJA1 gene, which encodes Cx43, exhibit modest developmental disorders resulting in a disease termed oculodentodigital dysplasia. Autosomal recessive mutations in the gene encoding Cx26 result in moderate to severe sensorineural hearing loss, whereas autosomal dominant mutations produce hearing loss and a wide range of skin diseases, including palmoplantar keratoderma. Here, we will focus on autosomal dominant mutations of the genes encoding Cx26 and Cx43 in relation to models that link genotypes to phenotypic outcomes with particular reference to how these approaches provide insight into human disease.

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“…This collection of studies has resulted in considerable debate as to how Cx26 is transported within mammalian cells during gap junction biogenesis. The importance of this debate has been elevated in recent years as it appears that the manifestation of human deafness in combination with etiologies of epidermal keratodermas depends extensively on the trans-dominant interactions of Cx26 mutants with other members of the connexin family (Bakirtzis et al, 2003;Forge et al, 2003;Marziano et al, 2003;Rouan et al, 2001;Thomas et al, 2004), possibly by co-oligomerization of the mutant with wild-type connexins while they co-reside within the same intracellular compartments. Likewise, the recent identification of Cx43 point mutations linked to oculodentodigital dysplasia (ODDD) (Paznekas et al, 2003;Richardson et al, 2004) has raised similar questions as to how Cx43 mutants may crosstalk with other members of the connexin family, including Cx26.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Cx43 and Cx26 transport to the plasma membrane and gap junction regeneration

Thomas

Jordan

Simek

et al. 2005

Journal of Cell Science

118

106

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Previous reports have suggested that Cx26 exhibits unique intracellular transport pathways en route to the cell surface compared with other members of the connexin family. To directly examine and compare nascent and steady-state delivery of Cx43 and Cx26 to the plasma membrane and gap junction biogenesis we expressed fluorescent-protein-tagged Cx43 and Cx26 in BICR-M1Rk and NRK cells. Static and time-lapse imaging revealed that both connexins were routed through the Golgi apparatus prior to being transported to the cell surface, a process inhibited in the presence of brefeldin A (BFA) or the expression of a dominant-negative form of Sar1 GTPase. During recovery from BFA, time-lapse imaging of nascent connexin Golgi-to-plasma membrane delivery revealed many dynamic post-Golgi carriers (PGCs) originating from the distal side of the Golgi apparatus consisting of heterogeneous vesicles and long, tubular-like extensions. Vesicles and tubular extensions were also observed in HBL-100 cells expressing a human, disease-linked, Golgi-localized Cx26 mutant, D66H-GFP. A diffuse cell surface rim of fluorescent-protein-tagged wild-type connexins was observed prior to the appearance of punctate gap junctions, which suggests that random fusion of PGCs occurred with the plasma membrane followed by lateral diffusion of connexins into clusters. Fluorescence recovery after photobleaching studies revealed that Cx26-YFP was more mobile within gap junction plaques compared with Cx43-GFP. Intriguingly, Cx43-GFP delivery and gap junction regeneration was inhibited by BFA and nocodazole, whereas Cx26-GFP delivery was prevented by BFA but not nocodazole. Collectively, these studies suggest that during gap junction biogenesis two phylogenetically distinct members of the connexin family, Cx43 and Cx26, share common secretory pathways, types of transport intermediates and turnover dynamics but differ in their microtubule-dependence and mobility within the plasma membrane, which might reflect differences in binding to protein scaffolds.

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The Effects of a Mutant Connexin 26 on Epidermal Differentiation

Cited by 22 publications

References 23 publications

Functional Domain Mapping and Selective Trans-dominant Effects Exhibited by Cx26 Disease-causing Mutations

Functional Domain Mapping and Selective Trans-dominant Effects Exhibited by Cx26 Disease-causing Mutations

Closing the Gap on Autosomal Dominant Connexin-26 and Connexin-43 Mutants Linked to Human Disease

Mechanisms of Cx43 and Cx26 transport to the plasma membrane and gap junction regeneration

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