Chromatin structure and developmental expression of the human alpha-globin cluster.

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• Human globin gene expression switches during development, from embryonic (zeta, epsilon) to fetal (gamma) and then adult (alpha, beta) chains.
• The alpha-like globin cluster includes the embryonic zeta-globin and adult alpha-globin genes.

Purpose of the Study:

• To investigate the chromatin structure and expression of the human alpha-globin gene cluster in fetal and adult erythroid cells.
• To determine if embryonic zeta-globin gene expression continues beyond the embryonic period.

Main Methods:

• DNase I hypersensitivity assays to map active chromatin regions.
• Nuclear runoff transcription assays to measure gene transcription rates.
• Immunofluorescence to detect zeta-globin protein production.

Main Results:

• DNase I hypersensitive sites were found at the 5' ends of alpha-globin genes and at the 5' end of the zeta-globin gene in fetal and adult erythroid cells.
• The entire zeta- to alpha-globin region showed sensitivity to DNase I digestion in late fetal erythroid cells.
• Nuclear runoff studies confirmed the presence of initiated polymerases on the zeta-globin gene in normal erythroid cells.
• Immunofluorescence detected zeta-globin protein in late fetal liver cells.

Conclusions:

• Active chromatin features are present in the zeta-globin region of fetal and adult erythroid cells.
• Embryonic zeta-globin gene transcription and protein synthesis continue at a low level in normal cells beyond the embryonic to fetal globin switch.