Marcogliese et al. 2018

Quick Summary

This 2018 paper was a major early step in understanding IRF2BPL-related disorder, now often called NEDAMSS. Before this report, IRF2BPL had not been clearly connected to a human Mendelian neurological condition. The researchers brought together seven people with damaging changes in the IRF2BPL gene and described the symptoms that seemed to connect them.

The paper showed that not all IRF2BPL changes looked exactly the same. Five people had truncating, or "stop," variants that likely shortened the IRF2BPL protein. These individuals had a more severe pattern that included developmental regression, seizures, low muscle tone, worsening coordination or ataxia, and other movement-related problems. Two people had missense variants, meaning one amino acid in the protein was changed. Their symptoms were described as milder overall, with developmental delay and seizures as the main features.

The researchers also studied the fruit fly version of the gene, called `pits`. These experiments supported the idea that IRF2BPL is important for the nervous system. In flies, reducing or disrupting the gene affected survival and nerve-cell health, and the human variants behaved in ways that supported their role in disease.

Why This Paper Matters

This paper matters because it helped establish IRF2BPL as a disease-associated gene. For families, that is a turning point. A child or adult who previously had unexplained developmental delay, seizures, regression, or movement symptoms could now potentially receive a more specific genetic diagnosis.

The paper also helped define an early clinical pattern. The researchers did not simply report one person with one variant. They collected seven affected individuals and compared their symptoms, genetic findings, and available medical testing. That made it possible to see that truncating IRF2BPL variants were associated with a more severe neurological course, while the two missense variants in this report appeared milder.

Another important part of the paper was the lab work. The authors did not rely only on genetic matching. They also studied the related gene in fruit flies to ask whether this gene is important in the nervous system. Those experiments supported the human findings and helped make the case that IRF2BPL disruption was not just a coincidence.

Compared with earlier knowledge, the new contribution was the connection between IRF2BPL and a recognizable neurological disorder. The paper helped move IRF2BPL from a gene with uncertain human relevance into the IRF2BPL/NEDAMSS story that later papers would expand.

What The Researchers Studied

The researchers studied seven people with neurological symptoms and rare damaging variants in IRF2BPL. This was a primary cohort paper, meaning the article reported affected individuals directly rather than only reviewing previously published cases.

The clinical information came from medical histories, neurological findings, genetic testing, and available supporting studies such as brain imaging, EEG, and other laboratory evaluations. Not every person had the same testing, and not every detail was available for every patient.

Genetically, the paper focused on heterozygous IRF2BPL variants. "Heterozygous" means one copy of the gene had the variant while the other copy was unchanged. Most variants were de novo when parental testing was available, meaning the variant was new in the affected person and was not inherited from either parent. The variants were identified through exome sequencing or similar genetic testing approaches and were confirmed by additional testing.

The paper also included functional studies in fruit flies. Fruit flies have a related gene called `pits`. The researchers studied where the fly gene was expressed, what happened when it was reduced or disrupted, and how human IRF2BPL variants behaved in experimental systems. These experiments were used to support the idea that IRF2BPL is needed for normal nervous-system function.

What Was Learned About Symptoms

The main clinical lesson from the paper was that IRF2BPL-related disorder can affect development, movement, seizures, and neurological function over time.

In the five people with nonsense or truncating variants, the clinical picture was more severe. These individuals had neurodevelopmental regression, meaning they lost skills after a period of development. Regression could involve motor skills, speech or communication, or broader developmental abilities. The paper described hypotonia, or low muscle tone, as part of the pattern. It also described progressive ataxia and lack of coordination, meaning movement could become less steady or less controlled over time.

Seizures were an important feature. The paper connected IRF2BPL variants with epilepsy or seizure disorders in multiple individuals. EEG testing was used in the clinical workup for some people, but the paper did not establish one single EEG pattern that defines the condition for everyone.

Movement symptoms were also important. In family-friendly terms, this means that some people had difficulty controlling body movements, balance, coordination, or walking. The paper emphasized progressive ataxia and poor coordination in the more severely affected group. Some individuals became more dependent on mobility support as their symptoms progressed.

Speech and communication were affected in some individuals. For some, this was part of global developmental delay. For others, regression meant that previously gained speech or language skills were reduced or lost. Swallowing and feeding issues can be part of the broader neurological picture in IRF2BPL-related disorder, but the details varied by patient and were not the same for everyone in this first cohort.

Cognition and learning were also affected. The two people with missense variants had global developmental delay, meaning delays across multiple developmental areas. In the truncating-variant group, the combination of developmental problems and regression suggested a more severe neurological course.

Brain MRI findings were variable. Some people with IRF2BPL-related disorder can have abnormal brain imaging, including changes that reflect effects on the brain or cerebellum, while others may have less specific or less striking imaging findings. This paper used available MRI information as part of the clinical description, but MRI alone was not presented as enough to diagnose or rule out the disorder.

One of the most useful messages from the paper is that the condition can look different depending on the type of variant. In this first group, truncating variants were linked with a more severe, regressive neurological pattern. The two missense variants were associated with developmental delay and seizures but were described as relatively milder than the truncating cases.

What Was Learned About Genetics

IRF2BPL is a gene that carries instructions for making a protein involved in gene regulation. Before this paper, IRF2BPL was not clearly known as a cause of a human neurological disorder.

The paper reported rare damaging variants in one copy of IRF2BPL. Most importantly, the variants were de novo when parental testing was available. This strengthened the evidence that the variants were related to the affected individuals' symptoms.

Five people had nonsense, or truncating, variants. A nonsense variant creates an early stop signal in the gene's instructions. In plain language, the cell may make a shortened protein, or it may reduce production from that copy of the gene. In this paper, truncating IRF2BPL variants were associated with the more severe group of symptoms, including regression, seizures, hypotonia, ataxia, and impaired coordination.

The truncating variants included changes such as `p.Glu172*`, `p.Arg188*`, `p.Gln126*`, and `p.Gln127*`. The asterisk means the variant creates a stop signal. The `p.Arg188*` variant was reported in two unrelated individuals, which added support that this was not a random finding.

Two people had missense variants: p.Pro372Arg and p.Lys418Asn. A missense variant changes one building block of the protein rather than creating an early stop signal. In this report, these two missense variants were associated with global developmental delay and seizures, with a milder overall picture than the truncating variants.

The researchers also looked at population genetic data. IRF2BPL appeared to be a gene that does not tolerate damaging variation well in the general population. That means harmful changes in the gene are uncommon among people who do not have related disease, which supports the idea that damaging IRF2BPL variants can have serious effects.

The fruit fly studies added another layer of evidence. The fly gene related to IRF2BPL was important for survival and nervous-system health. Experiments suggested that loss of function in this gene can harm neurons, and the human variants tested in the fly system behaved in ways consistent with disease relevance.

Patient And Cohort Details

The article described seven affected individuals. They were not all identical in age, symptoms, or disease course, but the group showed patterns that helped define the disorder.

The five individuals with truncating variants had the clearest shared pattern. They had neurological symptoms that included developmental regression, seizures, low muscle tone, worsening coordination, and ataxia. Several had loss of previously gained abilities. This group helped show that IRF2BPL-related disorder can be progressive, especially when the variant strongly disrupts the protein.

Two unrelated individuals had the same truncating change, p.Arg188Ter. Seeing the same rare variant in more than one affected person supported the connection between that variant and the neurological condition. Other truncating variants in the cohort included early stop changes such as p.Gln126Ter and p.Gln127Ter.

The two individuals with missense variants were different from the truncating group. One had p.Pro372Arg and one had p.Lys418Asn. Both had developmental delay and seizures, but their overall presentation was described as milder than the individuals with truncating variants. This helped introduce an early genotype-phenotype idea: different kinds of IRF2BPL variants may be linked with different levels of severity.

The patient details also showed why diagnosis can be difficult. Symptoms such as seizures, developmental delay, low tone, movement problems, and regression can occur in many neurological conditions. IRF2BPL could not have been recognized from symptoms alone. The genetic testing was essential for connecting these individuals.

The cohort was small, but it was powerful because the genetic and clinical findings pointed in the same direction. The paper also combined human patient data with fruit fly evidence, which made the case stronger than a simple case list.

What Families Can Take Away

This paper supports that IRF2BPL changes can cause a serious neurological condition affecting development, seizures, movement, and sometimes loss of skills. For families, it helps explain why a genetic diagnosis can bring together symptoms that may have seemed separate at first.

The paper also shows that IRF2BPL-related disorder can vary. Some people in this first cohort had severe regression and progressive movement problems. Others, especially the two people with missense variants in this report, had a milder picture focused on developmental delay and seizures. This means that the gene name alone does not predict every detail for every child or adult.

A practical takeaway is that developmental history matters. Whether a person gained and then lost skills, how seizures began, whether movement or coordination changed over time, and what MRI or EEG testing showed can all help the care team understand the individual's course.

Another takeaway is that this was not a treatment study. The paper did not test a specific medication, therapy, or management plan for IRF2BPL-related disorder. Medical decisions still belong with each person's clinicians, based on that person's symptoms, seizures, feeding and swallowing needs, mobility, communication, and overall health.

The paper gives families a foundation for understanding the diagnosis, but it does not define what every future will look like. Each person with an IRF2BPL variant is different, and later reports have continued to expand the known range of symptoms.

Limits Of The Paper

The main limit is size. The paper described seven people, which is very important for a newly recognized condition but still small. With only seven individuals, it cannot capture the full range of IRF2BPL-related disorder.

The comparison between truncating and missense variants was useful, but it was based on only five truncating cases and two missense cases. The pattern suggested that truncating variants may be more severe than missense variants, but later research is needed to understand genotype-phenotype relationships more completely.

The clinical data were not identical for every person. Some individuals had more detailed information than others. MRI, EEG, developmental history, swallowing or feeding information, and long-term follow-up were not equally complete across the cohort.

The paper did not prove which symptoms will appear in any one child or adult. It also did not establish a treatment, a prognosis, or a standard care plan. It described an association between IRF2BPL variants and neurological disease, supported by human genetics and fly experiments.

The fruit fly work was important, but animal models have limits. A fly model can show that a gene is important for nervous-system function and can help test whether variants are damaging. It cannot fully reproduce the human condition or predict exactly how symptoms will develop in a person.

Source Notes

* Article: IRF2BPL Is Associated with Neurological Phenotypes. * Citation details: Marcogliese et al. 2018; American Journal of Human Genetics; PMID 30057031; PMCID PMC6081494; DOI 10.1016/j.ajhg.2018.07.006. * Main text: clinical descriptions of seven affected individuals with IRF2BPL variants. * Main text: genetic results describing de novo heterozygous IRF2BPL variants. * Table 1: clinical characteristics and variant information for the seven subjects. * Figure 1: IRF2BPL variant positions and selected clinical or imaging information. * Functional sections and figures: Drosophila `pits` expression, loss-of-function, neuronal studies, and variant testing. * Supplementary Note: case reports for Subjects 1-7. * Supplementary Table 1: expanded clinical features for each subject. * Supplementary Table 2: prior clinical and laboratory evaluations. * Supplementary Table 3: exome sequencing methods and coverage details.