MITF and cell proliferation: the role of alternative splice forms

Bismuth, Keren; Maric, Dragan; Arnheiter, Heinz

doi:10.1111/j.1600-0749.2005.00249.x

Cited by 49 publications

(45 citation statements)

References 36 publications

(50 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This in vitro analysis with heterologous cells and overexpressed, cDNA-derived inducible proteins suggested that wild-type MITF has antiproliferative activities but that the lack of exon 2B, or the absence of phosphorylation at residue 73, yield MITF proteins lacking antiproliferative activity. The results confirm earlier findings with an S73A mutated protein analyzed in different cells (Bismuth et al 2005) and are consistent with the in vivo genetic observations that the relative increased accumulation of nonphosphorylatable MITF protein leads to increased melanoblast/melanocyte numbers, increases in the size and extent of pigmentation in certain heteroallelic combinations, and increased ability to compensate a strong dominantnegative allele, Mitf Mi-wh . …”

supporting

confidence: 79%

In Vivo Role of Alternative Splicing and Serine Phosphorylation of the Microphthalmia-Associated Transcription Factor

et al. 2012

Self Cite

View full text Add to dashboard Cite

The microphthalmia-associated transcription factor (MITF) is a basic helix-loop-helix leucine zipper protein that plays major roles in the development and physiology of vertebrate melanocytes and melanoma cells. It is regulated by post-translational modifications, including phosphorylation at serine 73, which based on in vitro experiments imparts on MITF an increased transcriptional activity paired with a decreased stability. Serine 73 is encoded by the alternatively spliced exon 2B, which is preferentially skipped in mice carrying a targeted serine-73-to-alanine mutation. Here, we measured the relative abundance of exon 2B + and exon 2B 2 RNAs in freshly isolated and FACS-sorted wild-type melanoblasts and melanocytes and generated a series of knock-in mice allowing forced incorporation of either alanine, aspartate, or wild-type serine at position 73. None of these knock-in alleles, however, creates a striking pigmentation phenotype on its own, but differences between them can be revealed either by a general reduction of Mitf transcript levels or in heteroallelic combinations with extant Mitf mutations. In fact, compared with straight serine-73 knock-in mice with their relative reduction of 2B + Mitf, forced incorporation of alanine 73 leads to greater increases in MITF protein levels, melanoblast and melanocyte numbers, and extent of pigmentation in particular allelic combinations. These results underscore, in vivo, the importance of the link between alternative splicing and post-translational modifications and may bear on the recent observation that exon 2B skipping can be found in metastatic melanoma.A LTERNATIVE splicing and post-translational modifications are among the major mechanisms by which individual genes generate multiple protein products. In fact, modern sequencing technologies and proteomic analyses have shown that most if not all multiexon pre-mRNAs give rise to alternatively spliced mature mRNAs (Nilsen and Graveley 2010) and that post-translational modifications modulate the activities of most eukaryotic proteins (Mann and Jensen 2003). In a simple sense, then, the two mechanisms are linked as post-translational modifications depend on the presence of the particular exons encoding the modifiable residues or proteolytic cleavage sites. Here, we present a mouse model that allows us to probe this link in vivo by separately targeting a splice site and a codon for a biologically relevant phosphoacceptor site in the gene encoding the pigment cell transcription factor, microphthalmia-associated transcription factor (MITF). In fact, pigmentation is particularly suitable for such studies as it provides for an easily visible and highly sensitive readout of gene function.Mitf plays a crucial role in the development and function of melanin-bearing pigment cells in skin, eye, and inner organs (Hodgkinson et al. 1993;Arnheiter et al. 2006;Arnheiter 2010). Its protein product is a basic helix-loop-helix leucine zipper transcription factor that regulates target gene promoters by binding specific E box...

show abstract

supporting

confidence: 79%

In Vivo Role of Alternative Splicing and Serine Phosphorylation of the Microphthalmia-Associated Transcription Factor

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…In epithelial cells, cyclin D1 and Myc, two proteins promoting cell proliferation, can be directly induced by b-catenin. In melanocytes, in addition to cyclin D1 and Myc another direct b-catenin target, Mitf-M, also controls cell proliferation (Bismuth et al, 2005;Carreira et al, 2005;Carreira et al, 2006;Garraway et al, 2005;Loercher et al, 2005). However, the only evidence that Mitf has a role in melanoblast proliferation in vivo is very indirect (Hornyak et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

Biological and mathematical modeling of melanocyte development

et al. 2011

View full text Add to dashboard Cite

SUMMARYWe aim to evaluate environmental and genetic effects on the expansion/proliferation of committed single cells during embryonic development, using melanoblasts as a paradigm to model this phenomenon. Melanoblasts are a specific type of cell that display extensive cellular proliferation during development. However, the events controlling melanoblast expansion are still poorly understood due to insufficient knowledge concerning their number and distribution in the various skin compartments. We show that melanoblast expansion is tightly controlled both spatially and temporally, with little variation between embryos. We established a mathematical model reflecting the main cellular mechanisms involved in melanoblast expansion, including proliferation and migration from the dermis to epidermis. In association with biological information, the model allows the calculation of doubling times for melanoblasts, revealing that dermal and epidermal melanoblasts have short but different doubling times. Moreover, the number of trunk founder melanoblasts at E8.5 was estimated to be 16, a population impossible to count by classical biological approaches. We also assessed the importance of the genetic background by studying gain-and lossof-function b-catenin mutants in the melanocyte lineage. We found that any alteration of b-catenin activity, whether positive or negative, reduced both dermal and epidermal melanoblast proliferation. Finally, we determined that the pool of dermal melanoblasts remains constant in wild-type and mutant embryos during development, implying that specific control mechanisms associated with cell division ensure half of the cells at each cell division to migrate from the dermis to the epidermis. Modeling melanoblast expansion revealed novel links between cell division, cell localization within the embryo and appropriate feedback control through b-catenin.

show abstract

“…Scansite also identified a weak match to the DEF-site in the same region, 188 CIFP 191 . Interestingly, residues 187-192 (ACIFPT) are encoded by an exon that is spliced out of one of the two common isoforms of MITF (66,67). Deletion of residues 187-192 (mimicking the alternative splice, and both removing the putative DEF-site and truncating the putative D-site) did not affect the binding of MITF to GST-ERK2 (data not shown).…”

Section: Erk2 and Mitf Co-immunoprecipitate From Hek293 Cells And Thmentioning

confidence: 99%

Characterization of an ERK-binding Domain in Microphthalmia-associated Transcription Factor and Differential Inhibition of ERK2-mediated Substrate Phosphorylation

Molina

Grewal

Bardwell

2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

Signal transduction networks that regulate gene expression and metabolism are crucial for cell growth, differentiation, and survival. Accordingly, aspects of the pathology of many diseases result from defects in signaling pathways or the transcriptional responses they regulate (1).Many extracellular signals are transmitted to downstream targets by an evolutionarily conserved protein kinase cascade designated the mitogen-activated protein kinase (MAPK) 2 cascade. The MAPK (also known as extracellular-signal-regulated kinase, or ERK) cascade is a three-kinase module that transmits signals from cell-surface receptors to downstream targets through sequential phosphorylations (2). The MAPK is phosphorylated, and thereby activated, by an upstream MAPK/ERK kinase (MEK), which has previously been activated by a MEK kinase, such as the proto-oncoprotein Raf. To further propagate the signal, activated MAPKs phosphorylate other kinases such as RSK1 (3), which then regulate downstream effectors. In addition, MAPKs directly phosphorylate many key effectors, including the ubiquitous transcription factors Elk-1, Ets-1, and ATF-2 (4 -6).Tissue-specific transcription factors are also targets of MAPK phosphorylation and provide cell-type specificity to MAPK-regulated responses (7,8). The microphthalmia-associated transcription factor (MITF) is a tissue-specific MAPK substrate found in melanocytes. MITF is a master transcriptional regulator for melanocytes, coordinating the expression of genes involved in stem cell maintenance, differentiation, melanogenesis, and cell survival (9 -11). MITF haploinsufficiency leads to Waardenburg syndrome type IIa, which is characterized by deafness and pigmentation defects caused by melanocyte loss in the inner ear and the skin (12). In addition, dominant-negative mutations in MITF are associated with another auditory-pigmentary disorder, Teitz syndrome (13, 14) (reviewed in Ref. 15). MITF is also a potential target in the treatment of skin cancer, because it may impart a selective advantage to melanoma cells at low expression levels (16, 17), while having an antiproliferative effect at higher expression levels (18).During the differentiation of neural crest-derived melanocytes, activation of the c-Kit receptor tyrosine kinase by its ligand Steel factor initiates signaling through the Ras3 Raf3 MEK1/23 ERK1/2 cascade, resulting in the phosphorylation of MITF, and the consequent induction of genes involved in differentiation (e.g. p21 Cip1 (19)), melanogenesis (e.g. tyrosinase (20)), and melanocyte survival (e.g. Bcl2 (16)). ERK2 directly phosphorylates MITF on Ser 73 (21); MITF is also phosphorylated at Ser 409 by ERK-activated RSK1 (22). The dually phosphorylated MITF displays increased affinity for the transcriptional co-activator CREB-binding protein (23). Dually phosphorylated MITF is also targeted for ubiquitination and subsequent degradation, ensuring transient gene induction (22).The ability of MAPKs to effectively and specifically recognize their substrates is enhanced by their capacity t...

show abstract

MITF and cell proliferation: the role of alternative splice forms

Cited by 49 publications

References 36 publications

In Vivo Role of Alternative Splicing and Serine Phosphorylation of the Microphthalmia-Associated Transcription Factor

In Vivo Role of Alternative Splicing and Serine Phosphorylation of the Microphthalmia-Associated Transcription Factor

Biological and mathematical modeling of melanocyte development

Characterization of an ERK-binding Domain in Microphthalmia-associated Transcription Factor and Differential Inhibition of ERK2-mediated Substrate Phosphorylation

Contact Info

Product

Resources

About