CACNA1E is an abbreviation of the gene's full name "CAlcium voltage-gated ChaNnel subunit Alpha 1E".

CACNA1E is one out of 20 000-25 000 genes in our body and plays a role in the communication between neurons in the brain. It is located on the short arm of chromosome 1 at position 25.3 and encodes the neuronal
R-Type CaV2.3 channel. This subunit helps to form the channel pore (hole) through which ions flow. A change in the gene changes the function of the channel and affects the release of neurotransmitters.

Normal calcium channels, without a mutation, open and closes regularly.

All previous studies showed that CACNA1E shows up as a "Gain of function" modification. 

This means that the calcium channel opens and stays open for a long time. As a result, calcium ion influx is increased, causing too much neuron excitability.

Mutations in CACNA1E causes a number of neurological phenotypes (=observable characteristics).

Most affected individuals present in infancy with epilepsy (refractory seizures, most commonly spasms) and developmental delay or no development at all. Many patients have joint contractures (hands or feet pull to the side - google: "ulnar deviation", clubbed feet, ...) and macrocephaly (a bigger head).

References:

Helbig Kathie, Lauerer Robert et al. (2018): De Novo Pathogenic Variants in CACNA1E Cause Developmental and Epileptic Encephalopathy with Contractures, Macrocephaly, and Dyskinesias. Am J Hum Genet. 2018 Nov 1;103(5):666-678. doi: 10.1016/j.ajhg.2018.09.006. Epub 2018 Oct 18.

The CACNA1E mutation is a rare disease. It is not known exactly how common it is because it has been known as a disorder only since 2018. It is estimated that this condition affects less than 1 in 100 000 children.

It is likely that some of the children who have a CACNA1E mutation have not been correctly diagnosed yet.
Due to new genetic techniques such as whole-exome sequencing, this diagnosis is likely to be made more often in children and adults.

More severe phenotypes of CACNA1E tend to occur brand new, or "de novo", not inherited from their parents.

Individuals with a de novo variant are the first individuals in their families to carry a disease-causing variant in CACNA1E. If a child is diagnosed de novo, the chance of having a future sibling that is affected by a CACNA1E mutation is expected to be very low. Many CACNA1E kids have healthy sisters and/or brothers!

picture credits: CACNA1E encephalopathy: a new calcium channel disease | Beyond the Ion Channel (epilepsygenetics.net)

In the gene can be found several transmembrane segments 1 to 6. Most of the people who show up with more severe symptoms have a genetic variant in a segment 6. Variants that are located outside of S6 may have a milder form of symptoms (e.g. no motor problems, can walk&talk, maybe "just" have epilepsy and/or autism
or all symptoms without epilepsy or even no symptoms at all...).