TGFB3 Human, Plant

What is TGFB3 and what is its fundamental role in human biology?

TGFB3 (Transforming Growth Factor Beta 3) is a member of the TGF-β superfamily defined by structural and functional similarities. It is secreted as a complex with LAP (Latency-Associated Peptide) and becomes active upon cleavage by plasmin, matrix metalloproteases, thrombospondin-1, and certain integrins. Once activated, TGFB3 binds with high affinity to TGF-β RII, a type II serine/threonine kinase receptor .

In humans, TGFB3 plays critical roles in cell differentiation, embryogenesis, and development. It primarily regulates molecules involved in cellular adhesion and extracellular matrix (ECM) formation during palate development. Without TGF-β3, mammals develop a deformity known as cleft palate .

How is TGFB3 expression regulated during development?

TGFB3 expression follows distinct developmental patterns, as demonstrated in zebrafish studies. It shows transient expression in the lens at 24 hours post-fertilization (hpf), but significant levels are not detected in the retina at 96 hpf when Müller glia (MG) are differentiating, nor at 7 days post-fertilization (dpf) .

By 10 dpf, TGFB3 RNA becomes detectable in the central retina where mature MG reside. This expression increases with age, with the adult pattern established by 3 months post-fertilization . These findings indicate developmental stage-specific regulation of TGFB3 expression, suggesting different functional roles throughout development.

What experimental approaches can validate TGFB3 function during development?

To validate TGFB3 function during development, researchers should consider multiple complementary approaches:

• Genetic knockdown using morpholino-modified antisense oligonucleotides

• Generation of knockout models using CRISPR/Cas9 genome editing

• Conditional expression systems using heat-shock or tissue-specific promoters

• Immunofluorescence with tissue markers (e.g., glutamine synthetase for MG)

• In situ hybridization to visualize spatial expression patterns

Studies in zebrafish have employed translation-blocking morpholinos and CRISPR/Cas9-generated mutants to investigate TGFB3's role in development. While TGFB3 knockdown did not affect MG differentiation as measured by glutamine synthetase expression, TGFB3-deficient fish exhibited smaller retinas and died around 2 weeks post-fertilization, indicating its essential role in development .

How do TGFB3 mutations contribute to human disease phenotypes?

TGFB3 mutations are associated with syndromic presentations of aortic aneurysms characterized by significant cardiovascular involvement, including thoracic/abdominal aortic aneurysm and dissection, and mitral valve disease . Clinical studies of 43 patients from 11 families with TGFB3 mutations revealed a spectrum of systemic features that overlap with Loeys-Dietz, Shprintzen-Goldberg, and Marfan syndromes .

These features include:

The broad clinical variability emphasizes the importance of early recognition due to high cardiovascular risk .

What is the paradoxical relationship between TGFB3 mutations and TGF-β signaling?

A fascinating aspect of TGFB3-related pathology is the observation of paradoxical up-regulation of both canonical and noncanonical TGF-β signaling in aortic wall tissues from patients with mutations . This finding is consistent with observations in patients with mutations in other TGF-β pathway components (TGFBR1/2, SMAD3, and TGFB2).

The paradox lies in the fact that loss-of-function mutations would theoretically reduce TGF-β signaling, yet tissue samples show increased expression of TGF-β ligands and enhanced pathway activation. This suggests complex compensatory mechanisms or disrupted negative feedback loops in TGF-β signaling that require further investigation to develop targeted therapies for aortic aneurysms .

How should researchers design experimental models to study TGFB3-associated diseases?

When designing experimental models for TGFB3-associated diseases, researchers should consider:

• Mutation type specificity - introduce precise human disease mutations rather than complete knockouts

• Tissue-specific effects - use conditional expression systems targeting relevant tissues

• Developmental timing - employ inducible systems to initiate mutations at appropriate stages

• Species differences - account for potential differences in TGFB3 function across species

• Compensatory mechanisms - examine expression of other TGF-β family members

The lethality observed in TGFB3-deficient zebrafish by 2 weeks post-fertilization highlights the importance of conditional approaches that allow study of TGFB3 function in adult tissues.

How does TGFB3 signaling differ from other TGF-β family members?

TGFB3 exhibits unique signaling properties compared to other TGF-β ligands. In zebrafish studies, forced expression of TGFB3, but not TGFB1b, suppressed injury-dependent MG proliferation, despite both ligands inducing pSmad3 expression (a marker of canonical TGF-β signaling) . This suggests TGFB3 activates additional non-canonical signaling pathways.

Experimental evidence indicates that PP2A and Notch signaling pathways act downstream of TGFB3 in maintaining cell quiescence . The ligand specificity in regulating cell proliferation highlights the importance of investigating TGFB3's unique signaling mechanisms beyond the canonical Smad-dependent pathway.

What methodological approaches can differentiate between canonical and non-canonical TGFB3 signaling?

To differentiate between canonical and non-canonical TGFB3 signaling pathways, researchers should employ multi-faceted experimental approaches:

These complementary approaches enable researchers to dissect the relative contributions of different signaling pathways downstream of TGFB3 activation.

How does TGFB3 expression correlate with regenerative capacity across species?

A compelling finding from comparative studies is that TGFB3 expression patterns differ between species with different regenerative capacities. TGFB3 is highly expressed by pro-regenerative MG in zebrafish retina but remains undetectable in non-regenerative MG of the mouse retina .

In the adult mammalian retina, TGF-β signaling is low, and TGF-β expression does not correlate with MG quiescence or proliferation. This contrasts with the zebrafish retina, where TGFB3 expression is tightly linked to MG quiescence, and its suppression is required for MG proliferation following injury .

Understanding these species-specific differences in TGFB3 expression and function could provide insights into enhancing regenerative capacity in mammals. Researchers should consider:

• Comparative transcriptomics across species with different regenerative abilities

• Cross-species transplantation experiments

• Targeted manipulation of TGFB3 expression in non-regenerative tissues

What are optimal techniques for studying TGFB3 expression and activity?

Effective study of TGFB3 requires multiple complementary techniques:

Zebrafish studies revealed that TGFB3 is expressed at least 80-fold higher than other TGF-β isoforms in quiescent MG, making it the predominant isoform in these cells . This highlights the importance of quantitative analysis when studying TGF-β family members.

How can researchers resolve contradictory findings in TGFB3 research?

The literature contains contradictory findings regarding TGFB3 expression and function. For instance, one study reported increased TGFB3 expression after retinal injury, while others found suppression at injury sites . To resolve such contradictions, researchers should:

• Use multiple complementary techniques to validate findings

• Consider spatial resolution (whole tissue vs. cell-specific expression)

• Examine temporal dynamics with finer time-point resolution

• Account for differences in experimental injury models

• Consider genetic background influences

• Provide detailed methodological information for replication

Additionally, different experimental approaches (transgenic expression vs. recombinant protein administration) may yield different results. One study found forced expression of Tgfb3 suppressed MG proliferation, while another reported that intravitreal injection of recombinant human TGFb1 enhanced MG reprogramming .

What considerations are important when designing TGFB3 knockout or mutation models?

When designing genetic models for TGFB3 research, researchers should consider:

• Complete knockout vs. specific mutations - TGFB3 null zebrafish die by 2 weeks post-fertilization , necessitating conditional approaches for studying adult functions

• Spatial specificity - use tissue-specific promoters to restrict modifications to tissues of interest

• Temporal control - employ inducible systems (e.g., heat shock promoters in zebrafish) to initiate modifications at specific developmental stages

• Compensatory mechanisms - examine expression of other TGF-β family members that might compensate for TGFB3 loss

• Readout specificity - include appropriate reporters to monitor effects on downstream signaling

Researchers have successfully generated TGFB3 mutants using CRISPR/Cas9, introducing frameshift mutations resulting in premature stop codons . This approach allows for detailed analysis of TGFB3 function in developing systems.

How do TGFB3 functions compare between humans and model organisms?

TGFB3 shows both conserved and divergent functions across species:

In humans, TGFB3 mutations cause syndromic aortic aneurysms with craniofacial and cardiovascular manifestations . In zebrafish, TGFB3 regulates MG quiescence and retinal regeneration . These differences highlight the importance of considering species-specific functions when translating findings across models.

Is there evidence for TGFB3 homologs or functional analogs in plants?

Based on the available search results, there is no specific information about TGFB3 homologs or functional analogs in plants. TGF-β family members are generally considered metazoan-specific signaling molecules, and canonical TGF-β signaling components are not typically found in plants.

Plants have distinct signaling pathways for regulating growth and development, such as auxin, cytokinin, and brassinosteroid signaling. Researchers interested in functional analogs might investigate growth-regulating signaling pathways in plants that serve developmental roles similar to TGF-β in animals.

This represents a significant knowledge gap in the comparative biology of TGF-β signaling across kingdoms.

How has evolutionary conservation of TGFB3 influenced its functional specificity?

While the search results do not provide comprehensive information about TGFB3 evolution, several observations suggest evolutionary insights:

• The presence of TGFB3 in both zebrafish and humans indicates conservation of the gene across vertebrate evolution

• Differential expression patterns (e.g., absent in mouse MG but present in zebrafish MG) suggest evolutionary divergence in regulation

• The essential role of TGFB3 in development across species (palate formation in mammals, retinal development in zebrafish) points to conserved developmental functions

Comparative genomic and functional studies across a broader range of species would help identify core conserved functions versus species-specific adaptations of TGFB3. This evolutionary perspective could provide insights into the fundamental roles of TGFB3 that have been maintained throughout vertebrate evolution.