June 2026 Research Update

Across this group of studies, researchers tested very different treatment ideas for Rett syndrome: changing how cells handle certain MECP2 genetic changes, adjusting brain and body signaling pathways in a Rett mouse model, and exploring anti-inflammatory or cannabinoid-based approaches in children. Overall, the strongest signals of symptom improvement came from preclinical (lab and animal) studies, while human evidence remained limited and mixed, with clear calls for better-quality clinical trials. [1] [2] [3] [4]

In a Rett syndrome mouse model, blocking a protein called PTP1B (either with selective allosteric inhibitors or by removing the gene) improved multiple problems, including muscle weakness, movement and coordination, and heart and breathing function. The improvements were linked to normalization of neurotrophic and metabolic signaling pathways (including TRKB and insulin/leptin signaling), suggesting PTP1B could be a disease-modifying target in animals. Effects were reported as sustained, including maintenance for over one year with genetic ablation. [1]

In cell-based experiments, anticodon-engineered transfer RNAs (ACE-tRNAs) were used to help cells read through certain MECP2 nonsense mutations so they could make full-length MeCP2 protein. These ACE-tRNAs restored key MeCP2 behaviors in cells, including proper localization in the nucleus and re-establishing interaction with the NCoR/SMRT complex via TBL1 recruitment, although efficiency varied by mutation and the work did not test long-term safety or delivery in living organisms. The authors noted that validation in a more realistic genomic context and additional safety assessment are needed before thinking about clinical translation. [2]

Human evidence in this set was exploratory. A systematic review of 17 studies of cannabinoid-based products in children and adolescents with autism spectrum disorder, fragile X syndrome, or Rett syndrome reported mostly mild-to-moderate side effects and low discontinuation, and it described seizure reduction in Rett syndrome, but concluded evidence is insufficient to support routine use and that randomized trials with standardized outcomes and long-term follow-up are needed. [3]

One case report described a single girl with clinically diagnosed Rett syndrome and difficult-to-control epilepsy who received long-term low-dose prednisolone with add-on methotrexate as an immunomodulatory approach alongside anti-seizure medicines. Over time, generalized seizures became infrequent and were replaced by brief focal events, and the report also noted improvements in behavior, sleep, and social interaction; however, the authors emphasized that a single case cannot prove the treatment caused the changes and that the child did not have genetic confirmation. Safety observations in this one patient included no clinically significant infections and stable monitoring tests with only mild liver enzyme elevations reported. [4]

For patients and caregivers, this month primarily adds background research about what future therapies might try to do: either correct certain MECP2-related protein problems at the cellular level, or improve broader movement, muscle, and breathing features by changing signaling pathways seen in Rett models. The mouse and cell results help identify targets and show biological effects, but they do not yet show that these approaches are safe or effective in people. The human-focused papers in this set (a review of cannabinoid studies and a single immunomodulatory case report) suggest possible effects on seizures and behavior in some situations, but uncertainty remains because the overall evidence is limited and not based on large, high-quality randomized trials in Rett syndrome. [1] [2] [3] [4]

Across these papers, Rett and Rett-like presentations did not always fit neatly into existing labels. One small adult series suggested some people can have a Rett diagnosis but fall outside typical or atypical categories, while a genetic case report showed that non-MECP2 gene changes can create a Rett-like picture, especially in males. [5] [6]

In a case series of five adults, the main features were movement-disorder symptoms (most often dystonia), and several had preserved social functioning and what the authors described as an essentially normal life. None met formal criteria for typical or atypical Rett syndrome, leading the authors to propose an additional label ("atypical atypical") and to suggest updating diagnostic criteria to include these uncommon patterns. [5]

In a report of two brothers and a review of 40 total published cases, changes in the IQSEC2 gene were linked to a Rett-like syndrome with intellectual disability, language impairment, and stereotypic movements, with regression not consistently present. Most reported cases were male, and the paper described patterns in where different variant types tended to occur within the IQSEC2 protein, as a first step toward understanding why symptoms vary between people. [6]

For families, these studies mainly serve as background about why a person may be described as having typical Rett, atypical Rett, or Rett-like features even when their day-to-day symptoms do not match classic expectations. They also underline that genetic causes beyond the most well-known Rett gene can produce similar symptoms, which can affect how clinicians talk about diagnosis and classification; however, these were small reports and do not establish new, widely accepted categories on their own. [5] [6]

Across these US real-world studies (based on insurance claims and linked pharmacy records), trofinetide use in Rett syndrome was not evenly distributed across the community. Uptake appeared concentrated in younger patients and those seen by specialists, and persistence after starting treatment was about half overall, with some people continuing for many months. The studies also point to certain health histories being linked with stopping earlier, but they cannot explain individual reasons for continuing or stopping. [7] [8] [9]

In a large analysis of 1,175 people who started trofinetide, 54.9% stayed persistent while 45.1% had a gap of 90 days or more between prescriptions. Most people remained on treatment beyond 3 months, and more than half continued through the available follow-up; among those who stopped, 7.6% later restarted. Older age and a history of infectious disorders were linked with a higher chance of non-persistence. [7]

When treated and untreated people with Rett syndrome were compared (766 treated vs 2,184 untreated), treated patients were younger on average (15.4 vs 23.5 years) and more often pediatric (66.6% vs 38.3%). Treatment was more often prescribed by child neurologists (50.3% vs 26.8%), and treated patients had more documented Rett-related features in claims, such as loss of acquired communication skills and loss of acquired motor skills. The authors noted that many adults and males remained untreated in this dataset. [8]

In the male-only analysis (51 treated and 415 untreated), most males identified with Rett syndrome were not treated with trofinetide. Among treated males, 52.9% were persistent, and the time-to-stop curve suggested about 70% stayed on treatment at least 6 months and more than half at least 17 months; pre-existing neurologic disorders were linked with non-persistence. Treated males also had higher recorded rates of epilepsy, feeding tube use, and respiratory failure than untreated males, suggesting the treated group may have had higher medical complexity. [9]

For families, this set of studies mainly provides context about how trofinetide has been used outside clinical trials in the United States: who tends to receive it, and how long people commonly stay on it in prescription data. These results do not show why any one person continues or stops (for example, benefit, side effects, access issues, or caregiver burden), and they do not measure symptom changes. The patterns may be most relevant for understanding real-world access and follow-up differences between children and adults and between females and males, while the reasons behind these differences remain uncertain. [7] [8] [9]

Across these studies, Rett-related brain changes look less like one uniform problem and more like several linked problems that depend on the cell type and brain region. In mouse models, certain inhibitory neurons and cerebellar Purkinje cells show strong early disruptions, and support cells (astrocytes) can also push neurons toward earlier-than-usual network stabilization. Separately, lab work suggests Rett mutations can alter how MeCP2 grabs onto DNA and how well it helps organize DNA packaging, which could help explain why symptoms vary across mutations. [10] [11] [12] [13] [14]

In the hippocampus (a brain area involved in learning and memory), gene activity changes were strongest in interneurons (inhibitory neurons), including a specific interneuron subtype marked by CHRM2, and a small shared set of gene changes appeared across sexes and early ages in Rett model mice. In female mosaic mice, some changes also showed up in nearby neurons that still had MeCP2, suggesting that MeCP2 loss in some cells can indirectly affect others. [10]

In the developing cortex, Mecp2-null astrocytes (support cells) released factors that sped up formation of perineuronal nets, a type of extracellular coating around neurons that is linked to reduced flexibility (plasticity) as circuits mature. The study saw higher levels of perineuronal-net-related components (including Hapln1 and Brevican) and signs of earlier maturation in Mecp2-null cortex, consistent with a shift toward earlier closure of developmental "critical periods." [12]

In the cerebellum, removing Mecp2 only from Purkinje cells did not broadly disrupt basic movement or social behavior in mice, but it did impair cerebellum-dependent motor learning and the normal learning-related firing patterns of Purkinje cells. The Purkinje cells also showed changes in structure, synaptic strength, and excitability that fit with less precise cerebellar output during learning. [11]

Two additional preclinical studies focused on DNA methylation and MeCP2 binding, which are upstream processes that can shape which genes are turned on or off. In a developing mouse brain atlas, nonstandard DNA methylation (mCH) rose quickly in the early postnatal period in a neuron-type-specific way, and MeCP2 loss particularly disrupted mCH patterns in GABAergic interneurons, which did not reach typical global mCH levels with age. [13]

In purified-protein lab experiments, full-length MeCP2 bound most strongly to double-stranded DNA but also bound DNA and RNA in other forms, and DNA methylation could stabilize binding when the usual DNA shape was missing. Rett-associated mutations fell into two mechanistic groups: mutations in the methyl-binding domain reduced methylation-dependent binding, while C-terminal mutations kept high binding strength but reduced cooperative interactions thought to support higher-order bridging. [14]

For patients and caregivers, these results mainly add background about what kinds of brain changes could sit underneath symptoms in Rett syndrome. They suggest that disrupted inhibitory neuron function, altered support-cell effects on circuit maturation, and cerebellar learning-signal changes may all contribute, and that the exact MeCP2 mutation could matter because it may change MeCP2 function in different ways. Because all of these are mouse or lab studies, it remains uncertain how directly each mechanism maps to day-to-day symptoms in people, and which changes are most important at different ages and in different brain regions.

This study links CDKL5 loss to altered timing and location of perineuronal net development in the visual cortex during a key developmental window. The overall pattern suggests earlier and region-specific changes in these extracellular structures, which can influence how flexible or "locked in" circuits become as they mature. [15]

At postnatal day 15, Cdkl5-null mice showed broadly increased perineuronal net staining intensity in pixel-level analyses across the visual cortex, consistent with earlier net-related changes. By postnatal day 30, the direction of change depended on the subregion, with lower overall net density in one area (V1M) but higher density of the strongest-intensity nets in another (V1B). [15]

The authors did not see strong left-right hemisphere differences overall, and the analysis was limited to males and to two ages, so it is unclear how these patterns look across development more broadly or in females. The work focuses on brain tissue markers rather than directly measuring vision or behavior in this report. [15]

For families affected by CDKL5-related disorder, this is early-stage animal research that helps describe one possible type of brain wiring change during development in the visual system. It matters mainly as background for understanding how developmental timing and circuit stabilization might be altered, but it does not yet tell us how strongly these net changes relate to specific symptoms in people or whether the same patterns occur across sexes and ages.

Across this month's research, one preclinical (animal) study suggests that changes in puberty timing and reproductive hormone signals can occur in a Rett syndrome mouse model, but the pattern differed by sex. Male mice showed delayed puberty along with lower levels of key reproductive hormones, while female mice did not show measurable differences in pubertal milestones in this study. Because this is animal research, it cannot confirm what happens in people, and it leaves open questions about how often or how strongly similar changes might appear in individuals with Rett syndrome. [16]

Male Mecp2-null mice reached a key pubertal milestone later than wild-type males and did so at a lower body weight. Blood testing showed lower luteinizing hormone and lower testosterone in these males, suggesting weaker signaling along the brain to pituitary to gonad hormone pathway during puberty in this model. [16]

In the same male mice, the number (density) of gonadotropin-releasing hormone (GnRH) neurons in part of the brain was higher, but circulating GnRH tended to be lower, pointing to a mismatch between neuron counts and measurable hormone levels in blood. The study also reported reduced testosterone-dependent nerve signaling (vasopressin-related innervation) in a specific brain region, which may reflect downstream effects of lower testosterone in this model. [16]

Female Mecp2-heterozygous mice did not show significant differences from controls in the timing of vaginal opening or in measures related to GnRH neurons in this study. The authors noted that later onset of symptoms in female mice could make puberty-related differences harder to detect at the time points studied. [16]

For patients and caregivers, this study mainly adds background evidence that Rett-related biology may affect puberty and reproductive hormone signaling, at least in some settings, and that effects could differ between males and females. Because the work was done in mice and focused on specific blood hormones and brain measurements, it does not show how common puberty or hormone differences are in people with Rett syndrome, what symptoms they might cause, or how they should be monitored. More human-focused research would be needed to understand whether similar patterns occur in real-world puberty and menstrual development, and how factors like nutrition, growth, and overall health interact with hormone changes.