PRICKLE1-related progressive myoclonus epilepsy with ataxia is a rare inherited condition characterized by recurrent seizures (epilepsy) and problems with movement. The signs and symptoms of this disorder usually begin between the ages of 5 and 10.

Problems with balance and coordination (ataxia) are usually the first symptoms of PRICKLE1-related progressive myoclonus epilepsy with ataxia. Affected children often have trouble walking. Their gait is unbalanced and wide-based, and they may fall frequently. Later, children with this condition develop episodes of involuntary muscle jerking or twitching (myoclonus), which cause additional problems with movement. Myoclonus can also affect muscles in the face, leading to difficulty swallowing and slurred speech (dysarthria).

Beginning later in childhood, some affected individuals develop tonic-clonic or grand mal seizures. These seizures involve a loss of consciousness, muscle rigidity, and convulsions. They often occur at night (nocturnally) while the person is sleeping.

PRICKLE1-related progressive myoclonus epilepsy with ataxia does not seem to affect intellectual ability. Although a few affected individuals have died in childhood, many have lived into adulthood.

PRICKLE1-related progressive myoclonus epilepsy with ataxia is caused by mutations in the PRICKLE1 gene. This gene provides instructions for making a protein called prickle homolog 1, whose function is unknown. Studies suggest that it interacts with other proteins that are critical for brain development and function.

Mutations in the PRICKLE1 gene alter the structure of prickle homolog 1 and disrupt its ability to interact with other proteins. However, it is unclear how these changes lead to movement problems, seizures, and the other features of PRICKLE1-related progressive myoclonus epilepsy with ataxia.

Normal Function

The PRICKLE1 gene provides instructions for making a protein called prickle homolog 1. The function of this protein is unclear, although it appears to play an important role in the development of the nervous system. Prickle homolog 1 is likely part of a chemical signaling pathway known as noncanonical Wnt signaling. During development before birth, noncanonical Wnt signaling helps to determine the position of various components within cells (cell polarity). This pathway also regulates the movement of nerve cells (neurons) in the developing nervous system.

Studies suggest that prickle homolog 1 interacts with other proteins, including RE1-silencing transcription factor (REST). The REST protein regulates several critical genes in neurons by turning off (suppressing) their activity. To regulate these genes, REST must enter the nucleus and attach (bind) to particular regions of DNA. Researchers believe that prickle homolog 1 controls REST by transporting it out of the nucleus, which prevents it from binding to DNA and suppressing gene activity. It remains unclear how the interaction between prickle homolog 1 and REST contributes to the normal development of the nervous system.

Health Conditions Related to Genetic Changes

PRICKLE1-related progressive myoclonus epilepsy with ataxia

At least three mutations in the PRICKLE1 gene have been identified in people with PRICKLE1-related progressive myoclonus epilepsy with ataxia. Each mutation changes a single protein building block (amino acid) in the prickle homolog 1 protein. One of the known mutations appears to disrupt the interaction between prickle homolog 1 and REST, blocking the transport of REST out of the nucleus. As a result, REST may inappropriately suppress certain genes in the developing nervous system. It is unclear how mutations in the PRICKLE1 gene lead to movement problems, seizures, and the other features of PRICKLE1-related progressive myoclonus epilepsy with ataxia.

Other Names for This Gene

• EPM1B
• FLJ31627
• FLJ31937
• MGC138902
• MGC138903
• PRIC1_HUMAN
• prickle homolog 1
• prickle-like 1
• REST (RE-1 silencing transcription factor)/NRSF (neuron-restrictive silencer factor)-interacting LIM domain protein
• REST/NRSF-interacting LIM domain protein
• RILP

Genomic Location

Some cases of PRICKLE1-related progressive myoclonus epilepsy with ataxia are inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Other cases of PRICKLE1-related progressive myoclonus epilepsy with ataxia are considered autosomal dominant because one copy of the altered gene in each cell is sufficient to cause the disorder. These cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

The prevalence of PRICKLE1-related progressive myoclonus epilepsy with ataxia is unknown. The condition has been reported in three large families from Jordan and northern Israel and in at least two unrelated individuals.