Neurochemical Research, Vol. 24, No. 5, 1999, pp. 637-641 Tubulin and Glial Fibrillary Acidic Protein Gene Expression in Developing Fetal Human Brain at Midgestation Utpal Pal,1 Sukanya Chaudhury,1 and Pranab K. Sarkar1,2 Developmental alterations in the expression of glial fibrillary acidic protein (GFAP) and A-tubu- lin were examined at the level of mRNA and protein in human fetal brain between weeks 13-23 of gestation. Except for a transient increase at week 15, GFAP expression in the cytoskeletal (CSK) fraction was low until week 17, when it increased steadily to week 23, corresponding to the phase of glial proliferation. The developmental profile of A-tubulin in the CSK fraction dis- played a biphasic pattern, with an initial rise between weeks 13-16 coinciding with the early phase of neuroblast multiplication, and a second rise between weeks 17-23 corresponding to the phase of glial proliferation. No significant difference in the spatial distribution of A-tubulin was found in different region of brain but GFAP expression varied with a higher level in cerebellum than that in cerebrum at late midgestation. KEY WORDS: Tubulin; glial fibrillary acidic protein; gene expression; human fetal brain. INTRODUCTION Tubulin and glial fibrillary acidic protein (GFAP), the major proteins of microtubules (1) and intermediate filaments (2) respectively, are components of the cy- toskeletal (CSK) system which are directly involved in growth and differentiation of neural cells. While GFAP represents a specific marker of astroglial cells, tubulin is a major structural component of the CSK proteins of both neuronal and glial cells. Accordingly, age-related changes in the accumulation of these proteins in the CSK fraction are correlated with the extent of differen- tiation and proliferation of the neural cells (3-5). Developmental patterns of tubulin and GFAP gene expression in animal models have been studied exten- sively (4-7) and it has been reported that in developing rat brain, tubulin and GFAP gene expression attain their 637 peaks postnatally, coinciding with the period of neu- ronal differentiation (8) or astroglial proliferation (5), respectively. Except for a report on increased expres- sion of GFAP in spinal chord of human fetal brain (8), no other information is available concerning GFAP gene expression in human fetal brain. Recently we re- ported an increase in actin gene expression together with accumulation of actin in the cytoskeletal fraction in developing human fetal brain between 16-19 weeks of gestation, corresponding to the initial phase of neu- ronal differentiation and synaptogenesis (9,10). In the present study, we report the pattern of tubu- lin and GFAP gene expression as well as their accu- mulation in the soluble (non-cytoskeletal) and insolu- ble (cytoskeletal) fraction in the cerebral prefrontal lobe of developing human fetal brain at midgestation. We have also tried to correlate the results with the phases of neuronal and glial proliferation. Previous re- ports indicate that human brain undergoes major form- ative changes during midgestation when critical events of neurite outgrowth and elongation leads to initiation of synaptoeenesis in human brain (11). It has also been (Accepted September 24, 1998) 0364-3190/99/0500-0637$16.00/0 © 1999 Plenum Publishing Corporation 1 Neurobiology Division, Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Jadavpur, Calcutta-700032, India. Tel : +91-33- 4724049; Fax : +91-33-4735197; E.mail : pkslab@giascl01.vsnl. net.in. 2 To whom to address reprint requests.