Skip to main page content
U.S. flag

An official website of the United States government

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2002 Aug 1;22(15):6526-36.
doi: 10.1523/JNEUROSCI.22-15-06526.2002.

Brain factor-1 controls the proliferation and differentiation of neocortical progenitor cells through independent mechanisms

Carina Hanashima  1 , Lijian Shen, Suzanne C Li, Eseng Lai
Affiliations

Brain factor-1 controls the proliferation and differentiation of neocortical progenitor cells through independent mechanisms

Carina Hanashima et al. J Neurosci. .

Abstract

The winged helix gene Brain factor-1 (BF1) has a pleiotropic role in the development of the cerebral hemispheres of the brain. Mice lacking BF1 have defects in the morphogenesis of the structures of the dorsal telencephalon (e.g., neocortex) and the ventral telencephalon (e.g., the basal ganglia). This study focuses on the functions of BF1 in the dorsal telencephalon. We showed previously that telencephalic progenitor cells lacking BF1 differentiate into neurons prematurely. Here, we demonstrate that the loss of BF1 also results in an early lengthening of the cell cycle in neocortical progenitors. To investigate the mechanisms by which BF1 regulates progenitor cell proliferation and differentiation in the developing brain, we have replaced the endogenous BF1 protein with a DNA binding defective form of BF1 in mice, BF1(NHAA). The BF1(NHAA) protein restores the growth of the dorsal telencephalon, by improving the proliferation of progenitor cells. However, the BF1(NHAA) protein does not correct the early neuronal differentiation associated with the loss of BF1. In contrast, replacement of endogenous BF1 with wild-type BF1 corrects the defects in both the proliferation and differentiation of neocortical progenitors. These results demonstrate that BF1 controls progenitor cell proliferation and differentiation in the neocortex through distinct DNA binding-independent and binding-dependent mechanisms.

PubMed Disclaimer

Figures

Fig. 1.
Fig. 1.
Targeting of the tetracycline transactivator (tTA) to the BF1 locus. A, Map of the targeting vector used to replace the BF1 gene in ES cells by homologous recombination. In the BF1 (+/− tTA) heterozygote at E13.5, the expression pattern of the tTA gene matches that of BF1 in the telencephalon (B, C) and olfactory epithelium (D, E), as detected by in situ hybridization. Mating of theBF1(+/−tTA) mice with a transgenic animal with a target gene under the control of multiple tetO sites results in offspring that express the target gene in BF1-expressing cells. An IRES–lacZ cassette placed downstream of the target gene directs translation of the β-galactosidase gene, which serves a reporter of target gene expression (F). Staining for β-gal activity in a BF1(+/−tTA):tetO-BF1NHAA IRES lacZ embryo at E13.5 demonstrates the expression of the target gene in the telencephalic neuroepithelium (H). No β-gal activity is detected in embryos lacking the tTA (G) or in BF1(+/−tTA): tetO- BF1NHAA IRES lacZ embryos harvested from pregnant dams that were fed doxycycline (20 μg/ml) in the drinking water (I). Scale bar, 200 μm.
Fig. 2.
Fig. 2.
Replacement of endogenous BF1 with BF1NHAA. Mating ofBF1(+/−lacZ):tetOBF1NHAA IRES lacZ males withBF1 (+/−tTA) females will yield offspring, one quarter of which will lack BF1. One half of these (or one eighth of the total) will also have the tetO BF1NHAAIRES lacZ construct. We refer to these as “NHAA rescue” embryos (E). Expression of theBF1NHAA transcript in these embryos was monitored by β-gal staining and by in situhybridization (B,#77; C, #99;D, #83). This was compared with the level of theBF1 transcript in BF1 (+/−) heterozygotes (A). The level of BF1NHAAprotein was determined by immunoblotting extracts from dissected telencephalon (#99 line) at E12.5, and compared with that in WT embryos, heterozygotes, and BF1 (−/−) mutants (F). Scale bar, 200 μm.
Fig. 3.
Fig. 3.
Improved growth of the dorsal telencephalon in NHAA and WT BF1 rescue embryos at E13.5. Coronal (A–D) and horizontal (E–H) sections show that the size of the dorsal telencephalon in the NHAA rescue is similar to that of the dorsal telencephalon in BF1 (+/−) heterozygotes and in the BF1 WT rescue. The NHAA rescue has a thicker cortical plate than that found inBF1(+/−) heterozygotes or in the BF1 WT rescue.Asterisks indicate the position of the cortical plate, which expresses β-galactosidase at lower levels than in the ventricular zone and contains the differentiated neurons of the dorsal telencephalon (F, H). dt, Dorsal telencephalon; bt, basal telencephalon. Scale bar, 200 μm.
Fig. 4.
Fig. 4.
Interkinetic nuclear migration of neocortical progenitors is not altered in the BF1 (−/−) mutant. Mitosis takes place at the apical surface, adjacent to the ventricle. Immunohistochemical localization of phosphorylated histone H3 demonstrates mitotic nuclei at the apical surface of the ventricular zone in the telencephalon of both normal BF1(+/−) heterozygotes and BF1(−/−) mutants at E13.5.
Fig. 5.
Fig. 5.
Aberrant pattern of BrdU labeling in the ventricular zone of the BF1 (−/−) mutant and restoration of normal patterns in the NHAA rescue. Diagram of the cell cycle in neocortical progenitor cells at E11.5 and E14.5 (I). Arrows depict the approximate position in the cycle of cells that will be labeled with BrdU after a single intraperitoneal injection of BrdU to the pregnant mouse. The position of this cohort of BrdU-labeled nuclei is also depicted 15 hr later, when the embryos are examined. When the cell cycle length is the same as the labeling period or slightly longer, labeled nuclei will be present in all phases of the cell cycle. Under these conditions, BrdU-labeled nuclei are distributed throughout the ventricular zone. This is observed from E11.5 to E13.5 in WT embryos (A–C) and at E11.5 in BF1 (−/−) mutants (E). When the cell cycle length increases to ∼15 hr or greater, labeled nuclei will be absent from the G2 and M phase of the cell cycle (I). This will result in a marked reduction in the number of BrdU-labeled nuclei at the apical surface of the ventricular zone, as seen at E14.5 in WT embryos (D) and at E12.5 to E14.5 inBF1 (−/−) mutants (F–H). In NHAA rescue embryos, 15 hr labeling at E13.5 (J) shows BrdU-labeled nuclei distributed throughout the ventricular zone, as found in normal embryos. BrdU-labeled nuclei are not excluded from the apical surface until E14.5 (K).Arrowheads point to the apical surface of the ventricular zone. Shown in this figure are high magnification views of the posterolateral region of the telencephalic neuroepithelium approximately at the positions indicated by thearrowheads in the horizontal sections of Figure 3. The posterior telencephalon is on the right side of each section.L, Quantitation of the percentage of BrdU-labeled nuclei at the apical surface of the ventricular zone in the posterolateral telencephalon, 15 hr following a single injection of BrdU from E11.5 to E14.5. Nuclei lining the ventricular surface were counted. The percentages of BrdU-labeled nuclei are plotted as the mean ± SEM. Scale bar, 50 μm.
Fig. 6.
Fig. 6.
The BF1NHAA protein improves the proliferation of telencephalic progenitors in the anterior telencephalon. Horizontal sections of E13.5 embryos fromBF1(+/−) heterozygotes (A–C),BF1(−/−) mutants (D–F), and NHAA rescue (G–I). The positions of higher magnification views of the anterior and posterior regions of the telencephalic neuroepithelium telencephalon are indicated withrectangles. J, The fraction of BrdU-positive nuclei after a 2 hr pulse of BrdU was determined in the anterior and posterior regions. The reduction in BrdU labeling in the anterior telencephalon of the BF1(−/−) mutant is corrected to near normal levels in the NHAA rescue. Scale bar:A, D, G, 400 μm;B, C, E, F,H, I, 50 μm.
Fig. 7.
Fig. 7.
Expression of the neuronal marker, MAP2, in the dorsal telencephalon at E12.5. MAP2 expression in coronal sections inBF1 (+/−) heterozygotes (A, D), NHAA rescue embryos (B, E), and BF1 WT rescue embryos (C, F) identifies differentiated cells of the preplate and cortical plate (mantle zone). The thickness of the mantle zone in the NHAA rescue is much greater than in the BF1heterozygote or in the BF1 WT rescue. The mantle zone:ventricular zone ratio is 0.15 in D, 1.4 inE, and 0.3 in F. The mantle zone is thinnest anteriorly and thicker posteriorly within the telencephalon. Therefore we show coronal sections from comparable planes at the level of the eye, in the heterozygote, the NHAA rescue, and theBF1 WT rescue. Scale bar: A–C, 400 μm;D–F, 50 μm.
Fig. 8.
Fig. 8.
Ectopic expression of Bmps is not corrected in the NHAA rescue. Bmp6(A–C) and Bmp7(D–F) expression is restricted to the dorsomedial telencephalic neuroepithelium in the BF1(+/−) heterozygote at E11.5 (arrows in A,D). In the BF1 (−/−) mutant and the NHAA rescue at E11.5, ectopic Bmp6 andBmp7 is detected in the lateral telencephalon. The level of Bmp6 andBmp7 is highest dorsolaterally and ventrolaterally (arrowheads). Scale bar, 200 μm.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Bourguignon C, Li J, Papalopulu N. XBF-1, a winged helix transcription factor with dual activity, has a role in positioning neurogenesis in Xenopus competent ectoderm. Development. 1998;125:4889–4900. - PubMed
    1. Caviness VJ, Takahashi T, Nowakowski R. Numbers, time and neocortical neuronogenesis: a general developmental and evolutionary model. Trends Neurosci. 1995;18:379–383. - PubMed
    1. Clark D, Mitra P, Wang S. Scalable architecture in mammalian brains. Nature. 2001;411:189–193. - PubMed
    1. Dewulf N, Verschueren K, Lonnoy O, Moren A, Grimsby S, Vande Spiegle K, Miyazono K, Hulebroeck D, ten Dijke P. Distinct spatial and temporal expression patterns of two type I receptors for bone morphogenetic proteins during mouse embryogenesis. Endocrinology. 1995;136:2652–2663. - PubMed
    1. Dou C, Li S, Lai E. Dual role of brain factor-1 in regulating growth and patterning of the cerebral hemispheres. Cereb Cortex. 1999;9:543–550. - PubMed

Publication types

MeSH terms