Mice are said to have empathy akin to that seen in humans.
This will leave you in awe but when it comes to empathy, mice are not left out in this special feeling.
Fear is said to be a key instinct just as predicting danger is a factor necessary for survival.
Coming to Empathy, it is said to be an innate behavior which makes mammals able to understand and share others fears, sorrows, joy and other emotions.

Recent studies show that altering genes can affect empathy-driven fear in mice; these studies have given us strong insights into the neurophysiologic mechanisms behind empathy. Varun Warrier, a Cambridge Ph.D. student suggested that decoding the genetic predispositions for empathy could help determine whether certain people respond better to particular therapies.
These studies done in Cambridge Univesity said that genes that control observational fear(empathy) is still unknown but with their study, mice whose Nrxn3 were sequenced(a misuse variant in neurexin) exhibited a remarkable selective enhancement in observational fear.

In a recent study, published on Institute for Basic Science, April 19, 2018, the mice used for these studies showed enhanced empathy when they were subjected to observing other mice receiving mild electric shocks. The observing mice behaved as if they were receiving the shocks themselves.
This demonstration of fear is similar to the affective-empathy observed in higher animals like humans.

In an exploratory clinical study, 18 strains of mice commonly used in laboratories where examined for observational fear. ‘’A Missense Variant at the Nrxn3 Locus Enhances Empathy Fear in the Mouse’’ Says Sehoon Keum.
Sehoon Keum further explained that ‘’It is not acquired only by directly experiencing a dangerous event, but also by observing others in threatening circumstances’’
One strain (the 129SI) was symbolically more empathic than the others. The sequencing of this gene enhanced fear in the observational mice.

After the sequencing of genomes; the researchers were able to discover a gene variant of Neurexin3 (Nrxn3). Nrxn3 is a protein that connects the neurons; it is evolutionally conserved among the vertebrates and it is abundant in some parts of the cortex of the human brain.
When these scientists artificially sequenced the variant, the mice that have a normal level of empathic-fear became more empathic and subsequently showed increased observational fear in their behaviors.

The scientists also observed that some specific neurons in the cerebral cortex (ACC) played a significant role in the observational fear. The ACC known as the anterior cingulate cortex has been previously known to be implicated in some fundamental cognitive processing and behavior.
These cognitive processes are social cognition, affective emotions and empathic response to fear. Furthermore, the ACC, the SST + Neurons work together to ensure many cognitive processes and their resultant effects are felt as increased or decreased empathic-fear.

Coming to the mechanism of action; the ACC and the neurons require Nrxn3 in order to accomplish its inhibitory functions during cognitive processing. In lieu of this, if the Nrxn3 gene is removed, then SST + neurons will release less GABA to the surrounding pyramidal neurons. GABA (Gamma-Aminobutyric Acid)is responsible for relieving anxiety, improving mood and controlling depression.  Looking at its function, this reduction in GABA causes an elevation in observational fear response just like the scientist observed in the mice fear-tests. The less release of GABA caused an increase in anxiety and tension.

This cascade of neurophysiologic mechanisms gives hope for therapeutic intervention of mental processing and mental disorders.