Subject(s)
Bacteriological Techniques/methods , Drug Monitoring/methods , Mycobacterium tuberculosis/isolation & purification , Staining and Labeling/methods , Tuberculosis, Pulmonary/microbiology , Adult , Antitubercular Agents/pharmacology , Antitubercular Agents/therapeutic use , Coloring Agents , Female , Humans , Microbial Viability/drug effects , Mycobacterium tuberculosis/physiology , Sputum/microbiology , Tuberculosis, Pulmonary/drug therapyABSTRACT
The Krox-20 gene encodes a zinc finger transcription factor, which has been shown previously, by targeted inactivation in the mouse, to be required for the development of rhombomeres (r) 3 and 5 in the segmented embryonic hindbrain. In the present work, Krox-20 was expressed ectopically in the developing chick hindbrain by use of electroporation. We demonstrate that Krox-20 expression is sufficient to confer odd-numbered rhombomere characteristics to r2, r4, and r6 cells, presumably in a cell-autonomous manner. Therefore, Krox-20, appears as the major determinant of odd-numbered identity within the hindbrain. In addition, we provide evidence for the existence of a non cell-autonomous autoactivation mechanism allowing recruitment of Krox-20-positive cells from even-numbered territories by neighboring Krox-20-expressing cells. On the basis of these observations, we propose that Krox-20 regulates multiple, intertwined steps in segmental patterning: Initial activation of Krox-20 in a few cells leads to the segregation, homogenization, and possibly expansion of territories to which Krox-20 in addition confers an odd-numbered identity.
