SLIT-ROBO Rho GTPase-activating protein 2 (srGAP2), also known as formin-binding protein 2 (FNBP2), is a mammalian protein that in humans is encoded by the SRGAP2 gene. [5] [6] It is involved in neuronal migration and differentiation [7] and plays a critical role in synaptic development, [8] brain mass and number of cortical neurons. [9] Downregulation of srGAP2 inhibits cell–cell repulsion and enhances cell–cell contact duration.
SRGAP2 dimerizes through its F-BAR domain. [10] SRGAP2C, a shortened version found in early hominins and humans that only has the F-BAR domain, antagonizes its action. It slows maturation of some neurons and increases neuronal spine density. [10]
SRGAP2 is one of 23 genes that are known to be duplicated in humans but not other primates. [11] SRGAP2 has been duplicated three times in the human genome in the past 3.4 million years: one duplication 3.4 million years ago (mya) called SRGAP2B, followed by two that copied SRGAP2B 2.4 mya into SRGAP2C and ~1 mya into SRGAP2D. All three duplications are also present in Denisovans and Neanderthals. [12] They are shortened in the same manner, keeping the F-box domain but ditching the RhoGAP and SH3 domains. [13] All humans possess SRGAP2C. [14] SRGAP2C inhibits the function of the ancestral copy, SRGAP2A, by heterodimerization and allows faster migration of neurons by interfering with filopodia production as well as slowing the rate of synaptic maturation and increasing the density of synapses in the cerebral cortex. [8] SRGAP2B is expressed at very low levels, and SRGAP2D is a pseudogene. Not all humans have SRGAP2B or SRGAP2D. [13]
The Disabled-1 (Dab1) gene encodes a key regulator of Reelin signaling. Reelin is a large glycoprotein secreted by neurons of the developing brain, particularly Cajal-Retzius cells. DAB1 functions downstream of Reln in a signaling pathway that controls cell positioning in the developing brain and during adult neurogenesis. It docks to the intracellular part of the Reelin very low density lipoprotein receptor (VLDLR) and apoE receptor type 2 (ApoER2) and becomes tyrosine-phosphorylated following binding of Reelin to cortical neurons. In mice, mutations of Dab1 and Reelin generate identical phenotypes. In humans, Reelin mutations are associated with brain malformations and mental retardation. In mice, Dab1 mutation results in the scrambler mouse phenotype.
Ras-related C3 botulinum toxin substrate 3 (Rac3) is a G protein that in humans is encoded by the RAC3 gene. It is an important component of intracellular signalling pathways. Rac3 is a member of the Rac subfamily of the Rho family of small G proteins. Members of this superfamily appear to regulate a diverse array of cellular events, including the control of cell growth, cytoskeletal reorganization, and the activation of protein kinases.
Tubulin alpha-1A chain is a protein that in humans is encoded by the TUBA1A gene.
Slit homolog 2 protein is a protein that in humans is encoded by the SLIT2 gene.
Roundabout homolog 1 is a protein that in humans is encoded by the ROBO1 gene.
Synaptic Ras GTPase-activating protein 1, also known as synaptic Ras-GAP 1 or SYNGAP1, is a protein that in humans is encoded by the SYNGAP1 gene. SYNGAP1 is a ras GTPase-activating protein that is critical for the development of cognition and proper synapse function. Mutations in humans can cause intellectual disability, epilepsy, autism and sensory processing deficits.
Baculoviral IAP repeat-containing protein 1 is a protein that in humans is encoded by the NAIP gene.
CDK5 regulatory subunit-associated protein 2 is a protein that in humans is encoded by the CDK5RAP2 gene. It has necessary roles in the formation and stability of microtubules from the centrosome and has been found to be linked to human brain size variation in males. Multiple transcript variants exist for this gene, but the full-length nature of only two has been determined.
Slit homolog 1 protein is a protein that in humans is encoded by the SLIT1 gene.
SLIT-ROBO Rho GTPase-activating protein 3 is an enzyme that in humans is encoded by the SRGAP3 gene.
Dock7, also known as Zir2, is a large protein involved in intracellular signalling networks. It is a member of the DOCK-C subfamily of the DOCK family of guanine nucleotide exchange factors (GEFs) which function as activators of small G proteins. Dock7 activates isoforms of the small G protein Rac.
Homeobox protein EMX1 is a protein that in humans is encoded by the EMX1 gene. The transcribed EMX1 gene is a member of the EMX family of transcription factors. The EMX1 gene, along with its family members, are expressed in the developing cerebrum. Emx1 plays a role in specification of positional identity, the proliferation of neural stem cells, differentiation of layer-specific neuronal phenotypes and commitment to a neuronal or glial cell fate.
SLIT-ROBO Rho GTPase-activating protein 1 is an enzyme that in humans is encoded by the SRGAP1 gene.
The Roundabout (Robo) family of proteins are single-pass transmembrane receptors that are highly conserved across many branches of the animal kingdom, from C. elegans to humans. They were first discovered in Drosophila, through a mutant screen for genes involved in axon guidance. The Drosophila roundabout mutant was named after its phenotype, which resembled the circular traffic junctions. The Robo receptors are most well known for their role in the development of the nervous system, where they have been shown to respond to secreted Slit ligands. One well-studied example is the requirement for Slit-Robo signaling in regulation of axonal midline crossing. Slit-Robo signaling is also critical for many neurodevelopmental processes including formation of the olfactory tract, the optic nerve, and motor axon fasciculation. In addition, Slit-Robo signaling contributes to cell migration and the development of other tissues such as the lung, kidney, liver, muscle and breast. Mutations in Robo genes have been linked to multiple neurodevelopmental disorders in humans.
T-box, brain, 1 is a transcription factor protein important in vertebrate embryo development. It is encoded by the TBR1 gene. This gene is also known by several other names: T-Brain 1, TBR-1, TES-56, and MGC141978. TBR1 is a member of the TBR1 subfamily of T-box family transcription factors, which share a common DNA-binding domain. Other members of the TBR1 subfamily include EOMES and TBX21. TBR1 is involved in the differentiation and migration of neurons and is required for normal brain development. TBR1 interacts with various genes and proteins in order to regulate cortical development, specifically within layer VI of the developing six-layered human cortex. Studies show that TBR1 may play a role in major neurological diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and autism spectrum disorder (ASD).
Slit is a family of secreted extracellular matrix proteins which play an important signalling role in the neural development of most bilaterians. While lower animal species, including insects and nematode worms, possess a single Slit gene, humans, mice and other vertebrates possess three Slit homologs: Slit1, Slit2 and Slit3. Human Slits have been shown to be involved in certain pathological conditions, such as cancer and inflammation.
Slit-Robo is the name of a cell signaling protein complex with many diverse functions including axon guidance and angiogenesis.
SLIT-ROBO Rho GTPase activating protein 2C is a protein in humans that is encoded by the SRGAP2C gene.
ARHGAP11B is a human-specific gene that amplifies basal progenitors, controls neural progenitor proliferation, and contributes to neocortex folding. It is capable of causing neocortex folding in mice. This likely reflects a role for ARHGAP11B in development and evolutionary expansion of the human neocortex, a conclusion consistent with the finding that the gene duplication that created ARHGAP11B occurred on the human lineage after the divergence from the chimpanzee lineage but before the divergence from Neanderthals.
Tet methylcytosine dioxygenase 3 is a protein that in humans is encoded by the TET3 gene.