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Federico Calegari Group

Proliferation and Differentiation of Neural Stem Cells

Portrait Federico Calegari


The Calegari Group’s goal is to promote the expansion of endogenous neural stem cells (NSC) to improve the function of the mammalian brain.

It’s just a matter of Time: How to give the brain more neurons and protect Earth from Mars Attacks

NSC, like any other stem cell, can divide to generate two identical stem cells or differentiated progeny, such as neurons. We found that shortening the cell cycle of NSC induces them to expand, more than they usually do. As a result, they can generate more neurons. In turn, manipulating the Time of NSC allows us to generate mice with bigger brains, hence, smarter. Let’s us get into the details of this …

In the developing brain, a lengthening of the G1 phase of the cell cycle of NSC is necessary and sufficient to induce their switch from proliferation to differentiation (Salomoni & Calegari, 2010; Fig. 1A). Thus, all we need to do to expand NSC is to force them to cycle Fast & Furious. Christian did that by overexpressing Cdk4/cyclinD1 (4D) and, luckily for his PhD and my tenure evaluation, this worked quite well resulting in mice born with more neurons (Lange et al., 2009).

So far so good, we can generate mice with more neurons. But can we generate mice with folded brains and gyri like the human brain??? That was a project we could not resist, the problem was to find a student buying all that crap. We achieved the latter by recruiting Miki and making her an offer she could not refuse. The rest was downhill. Miki generated a dual-transgenic, tissue-specific, inducible and reversible 4D line, which resulted in a brainy mouse, which, needless to say, was called Miki Mouse (Nonaka et al. 2013). However, as big as these brains were, we couldn’t get any gyrus out of them (Fig. 1B). How did gyri emerge during evolution? Was Miki Mouse proof of Intelligent Design? To find this out, we teamed up with Victor’s group and expanded ferret NSC absent in mouse to finally get new gyri and folds (Nonaka et al., 2013).

Yet, the problem was to find editors, and creationists alike, to get the story published. We tried many Journals but they kept criticizing the lack of novelty given that “viruses to expand NSC were known to increase brain size and cognitive function in monkeys” (Wyatt et al. The Rise of the Planet of the Apes. Century Fox’s, 2011). So we changed our story by criticizing Wyatt’s report for the poor description of methods and noting that, in contrast to the aggressive monkeys, both Miki Mouse and Victor’s ferrets were well-behaved and never attacked any students. In turn, this suggested that gyrification correlates with megalomaniac behavior as fully supported by two hyper-aggressive and super-gyrified species: humans on this planet and Martians on our neighboring planet (Burton et al., Mars Attacks, 1996) (Fig. 1C). Victor and I could not allow those green midgets to invade us again, so we published a paper describing the Achilles’ heel of the Martians’ brain, and saved the world (Borrell & Calegari, 2014).

Development is interesting and fun but adult stem cells are interesting, fun, and useful (so everybody say …). Therefore, Benedetta used 4D to generate extra neurons in the adult brain by the overly complicated stereotaxic injection of tissue-specific, temporarily-controlled, tamoxifen-dependent ubb::GFPloxNLS-T2A-Cdk4-T2A-Ccnd1lox HIV-lentiviruses in C57BL/6J nestin::CreERT2 mice (… if you got that, you already deserved your PhD!). To cut it short, it worked (Artegiani et al., 2011) allowing Sara to improve the sense of smell (Bragado et al., 2019) (Fig. 1D) and Gaby to use a similar, but more colorful method (Fig. 1E) to make old mice remember how to feel young again (Berdugo et al., 2020). Since we like movies (you should have guessed by now), I made two videos of those two papers. Click on YouTube and enjoy (Sara’s; Gaby’s; Fig. 1F).

Federico Calegari Research: Figure
Figure 1 (A) progenitors undergoing different division have different G1 length. (B-D) plasmids used to manipulate G1 length (B) by in utero electroporation (C) resulting in increased progenitors expansion and thicker germinal zones (D) (Lange et al., 2009). These experiments corroborated the cell cycle length hypothesis (Calegari and Huttner, 2003; Salomoni and Calegari, 2010; Lange and Calegari, 2010) (E). (F-G) Manipulation of G1 by 4D was used to increase cortical surface area in mouse (F) and gyrification in ferret (G; red lines). (G-H) 4D and control viral constructs (if you understand what are all those abbreviations you already deserve a PhD!) (G) delivered in the adult hippocampus (H). (I) This allowed us to switch neurogenesis On and Off. (J) We plan to use that to solve all mysteries in science (iPhone not depicted for copyright issues).

Future Projects and Goals

If you endured reading thus far, and could understand more than the average editor usually does, then you must be able to guess our future ambitions. Among these, is to expand NSC to rescue brain function in disease and, even more challenging, understand how can our 4D-neurons improve the computational performance the most sophisticated machine in the universe that we know: the brain.

Methodological and Technical Expertise

We have a lot of fun trying to develop new tools and techniques. You might be surprised to know that from time to time some also work. These are some of those we have contributed in the past (omitted are those that “did not work” as the students keep telling me without giving any detail).

  • a whole-embryo culture system to grow mouse embryos without their mothers (Calegari and Huttner, 2003).
  • a system to overexpress/knockdown genes in NSC by electric shocks (among others: Calegari et al., 2002; Lange et al., 2009).
  • Viral-infections in all flavors and colors (Artegiani et al., 2011; Artegiani and Calegari, 2013).
  • Methods to control gene expression in whole organisms by UV light (Cambridge et al., 2009), monitor miRNA activity live (DePietri et al., 2006), check miRNA targets (Ghosh et al., 2014) and catch transcription factors in the act (Artegiani et al., 2014)
  • Any sort of transgenic mouse, can’t even remember them all. I only know that the bill from the animal house is horrendous. The latest one is a cool red and green mouse made by Silvia and used by Juli to sequence non-coding transcripts of NSC (Aprea et al., 2013) … and yes we go wild about sequencing (Aprea et al., 2015)


since 2015
Professor for Proliferation of Mammalian Neural Stem Cells

since Nov 2006
Group leader CRTD, Dresden

Staff scientist, MPI-CBG, Dresden

Postdoctoral fellow, MPI-CBG, Dresden

Ph.D., University of Milano Italy

Visiting scientist, University of Heidelberg

Master’s Degree, University of Milano Italy

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Calegari Group at TUD CRTD

Selected Publications

Artegiani B, de Jesus Domingues AM, Bragado Alonso A, Brandl E, Massalini S, Dahl A and Calegari F
Tox: A multifunctional transcription factor and novel regulator of mammalian corticogenesis.
EMBO J, 34:896–910 (2015)

Aprea J, Prenninger S, Dori M, Sebastian Monasor L, Wessendorf E, Zocher S, Massalini S, Ghosh T, Alexopoulou D, Lesche M, Dahl A, Groszer M, Hiller M and Calegari F
Transcriptome sequencing during mouse brain development identifies long non-coding RNAs functionally involved in neurogenic commitment.
EMBO J, 32:3145–60 (2013)

Nonaka-Kinoshita M, Reillo I, Artegiani B, Martinez M, Nelson M, Borrell V and Calegari F
Regulation of cerebral cortex size and folding by expansion of basal progenitors.
EMBO J, 32:1640 (2013)

Artegiani B, Lindemann D and Calegari F
Overexpression of cdk4 and cyclinD1 triggers a greater expansion of neural stem cells in the adult mouse brain.
J Exp Med 208:937–948. (2011)

Lange C. Huttner W.B. and Calegari F.
Cdk4/cyclinD1 overexpression in neural stem cells shortens G1, delays neurogenesis, and promotes the generation and expansion of basal progenitors.
Cell Stem Cell 5:320–31 (2009)


Center for Regenerative Therapies Dresden (CRTD)
TU Dresden
Fetscherstraße 105
01307 Dresden