HTR4 gene structure and altered expression in the developing lung.

Area of Science:

• Genomics
• Molecular Biology
• Respiratory Medicine

Background:

• Genome-wide association studies (GWAS) identified single nucleotide polymorphisms (SNPs) in the 5-hydroxytryptamine receptor 4 (5-HT₄R) gene (HTR4) associated with lung function.
• Understanding the role of HTR4 in lung physiology is crucial for interpreting these genetic associations.

Purpose of the Study:

• Investigate HTR4 gene and 5-HT₄R protein expression in adult and fetal lung tissues and cultured airway cells.
• Define the HTR4 gene structure, particularly at the 5' end.
• Explore potential functional implications of key HTR4 SNPs using bioinformatics.

Main Methods:

• Quantitative PCR (Q-PCR) and reverse transcription PCR (RT-PCR) with 5' rapid amplification of cDNA ends (5' RACE) for gene expression and structure analysis.
• Immunohistochemistry (IHC) and radioligand binding assays for protein expression analysis.
• Bioinformatic analysis of public gene expression data (microarrays) and regulatory elements (ENCODE).

Main Results:

• Low 5-HT₄R protein expression observed in adult lung, primarily in alveolar pneumocytes; differential expression noted in fetal lung development.
• HTR4 mRNA levels were low in adult lung tissue and cultured airway cells (HASM, HBEC) compared to brain.
• Bioinformatic analysis revealed HTR4 SNPs associated with regulatory elements for transcription factors involved in lung development, such as Foxp1.

Conclusions:

• The 5-HT₄R gene (HTR4) plays a role in lung development.
• The identified genetic variations and expression patterns of HTR4 may contribute to the observed associations with lung function.