Neuroblasts: the precursors of nerve cells

During the generation of nerve tissue, these cells are transformed into neurons and neuroglia.

Today the term neuron is widely known to most of the population. We know that it is the main type of cell that is part of our nervous system, being the basic unit of this system, and that they transmit bioelectrical impulses throughout the system in order to transfer orders or information to the different parts of our organism.

But, do we know how or from what they arise? At what moment of our development do they appear? The answer to these questions lies in the neuroblasts.which we are going to know throughout this article.

Neuroblasts: what are they?

Neuroblasts are a type of embryonic cell of ectodermal origin that is characterized as the precursor of nerve cells, specifically neurons and neuroglia.specifically neurons and neuroglia.

It is a type of cell that appears during gestation, born in the neural plate from ectoderm tissue to begin to mature and migrate towards their final location and end up shaping our nervous system.

Neuroblasts are especially active and visible during gestation, diminishing greatly after birth although they may still be active. It is the immediate precursor of the neuron, transforming into it after a maturation process.

The development of the nervous system

As we have said, neuroblasts are embryonic cells, which are produced during the gestation of a future individual. Before nerve tissue can form, some development has had to take place in the fetus. certain development has had to take place in the fetus and neurulation has and neurulation to begin.

This occurs approximately at the third week after fertilization. At this time the ectoderm is stimulated to eventually generate the neuroectoderm, until the neural plate is generated.

This plate, a layer of initially epithelial cells (which will be called matrix cells), will proceed to grow and expand in a cephalocaudal manner and will generate folds, in which ectodermal cells will begin to differentiate. The plate will close on itself generating the so-called neural tube, which will end up closing its ends during the fourth week.

The cells of the matrix are directed towards the cavity or hollow area of the tube and, at this point, proceed to divide and replicate continuously, which will cause the neural tube to increase in size. The first neuroblasts will begin to mature and form as such, losing the ability to replicate (with small exceptions) and can only finish maturing to become a mature nerve cell.

From this moment on, the neuroblast will proceed to migrate towards its final location, the point at which it will eventually transform into a neuron. Generally, the older the neuron, the greater the depth at which it will be found.

An example of this can be seen in the spinal cord. Once formed, the neuroblasts begin to migrate towards the periphery of the neural tube, reaching the so-called intermediate zone.Once formed, the neuroblasts begin to migrate towards the periphery of the neural tube, reaching the so-called intermediate zone which will end up being the gray matter of the medulla, where they will begin to mature and grow peripherally until they generate the marginal zone (future white matter). Other cell types will also be generated by the matrix, such as glial cells and microglia.

Neuron formation

The neuroblast does not become a neuron immediately, but requires a maturation process to be able to form it. Initially, the cell from which the neuroblast and future nerve cell will be formed has a nucleus and a protodendrite. possesses a nucleus and a protodendriteand a protodendrite, being inserted in the wall of the neural plate. However, at the moment of migrating towards the cavity to start replicating, it loses this dendrite, becoming an apolar spherical nucleus.

Once the replication process is completed and as the neuroblast begins to form as such, two opposing prolongations progressively appear, forming something similar to a bipolar neuron. One of these prolongations elongates and will eventually become an axon, while the other fragments to generate the future dendrites. These elements will mature over time to form an adult neuron.

Do they exist in adults?

Although it was previously thought that neuroblasts could only be found in gestation and in the first years of life, with the discovery of adult neurogenesis in some regions of the brain, it has been it has been possible to observe how neuroblasts are formed in some regions throughout our lives, especially in the subventricular zone of the third ventricle and in the hippocampal gyrus.

These neuroblasts are mainly directed to the olfactory bulb or to the hippocampus itselfThese neuroblasts are mainly directed to the olfactory bulb or to the hippocampus itself, to generate inhibitory neurons of the GABAergic or excitatory glutamatergic type, and allow them to maintain a large number of functions.

The neurogenesis involved in their existence is fundamental to allow mental plasticity, learning, and stimulus discrimination. At the level of pathology, it can allow the overcoming of strokes, cerebrovascular accidents and trauma and the at least partial recovery of lost functions.

Potential problems and associated diseases

Given that neuroblasts are the step prior to the existence of neurons, we are dealing with one of the most relevant embryonic cell types for our development. However, as with all cell types, we may encounter different problems during their generation and maturation.

It is possible that neuroblasts fail to mature to form complete neurons, that there is an uncontrolled growth, that there is an uncontrolled growth, that there is an uncontrolled growth.It is possible that neuroblasts fail to mature to form complete neurons, that there is uncontrolled, sudden and detrimental growth in their number, that they do not migrate to the areas where their existence would be necessary or that for some reason there are not enough in the organism.

The causes of these alterations can be acquired, but considering that a large part of neuroblast formation and migration occurs during gestation, it is much more likely that the cases are due to genetic disorders, problems during fetal gestation or the appearance of mutations.

Two examples of disorders that are linked to neuroblasts can be found in the the presence of anencephaly or the existence of malignant tumors linked to these cells known as neuroblasts. linked to these cells known as neuroblastomas.

Bibliographic references:

• Snell, R.S. (2007). Clinical Neuroanatomy. 6th edition. Editorial Médica Panamericana. Madrid, Spain.
• López, N. (2012). Biología del desarrollo. Workbook. McGraw Hill.