Developmental aspects of chromatin structure and gene expression

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• Globin genes are crucial for oxygen transport and their regulation is complex.
• Hypersensitive sites in DNA are associated with gene activity and chromatin structure.
• Understanding these sites' role in development and inheritance is important.

Purpose of the Study:

• To investigate the conformational basis of globin-associated hypersensitive sites.
• To determine the developmental relevance of these sites in avian and human cells.
• To explore the propagation and inheritance mechanisms of hypersensitive sites.

Main Methods:

• DNaseI digestion assays to identify hypersensitive sites.
• S1 nuclease mapping to assess DNA single-strandedness.
• Methylation analysis in sperm.
• Chromatin structure analysis in fetal and adult erythropoietic tissues.

Main Results:

• DNaseI-hypersensitive sites can propagate their structure to daughter cells independently of initial triggers.
• Single-stranded DNA character at hypersensitive sites may explain their propagation.
• Hypersensitive sites in an avian retrovirus remain unmethylated in sperm, suggesting germline transmission.
• Human beta-globin gene cluster shows specific DNaseI cuts in erythroid cells, with sites near CAP sites.
• Fetal cells have hypersensitive sites at all four globin genes (G gamma, A gamma, delta, beta); adult cells show sites only for delta and beta genes.

Conclusions:

• Hypersensitive sites possess self-propagation capabilities, potentially via single-stranded DNA structures.
• Structural information at hypersensitive sites may be transmitted from germline to offspring.
• Developmental changes in human globin gene expression, particularly delta and beta, involve modulation of these hypersensitive sites.