MECP2 germline mosaicism plays an important part in the inheritance of Rett syndrome: a study of MECP2 germline mosaicism in males

Orthopedic Conditions and Interplay with Functional Abilities and MECP2 Variant Subtype in Rett Syndrome Patients

PURPOSE

Rett syndrome (RTT) is a rare multi-systemic disorder primarily linked to mutations in MECP2 gene. This study aims to describe the prevalence of orthopedic conditions in RTT patients, and examine their intricate interplay with functional capabilities, and MECP2 variant subtypes.

METHODS

Conducted as a cross-sectional retrospective observational study, the research encompassed 55 patients meeting clinical RTT criteria and holding MECP2 mutations. A review of clinical records was performed to gather demographic data, mutation subtypes, orthopedic conditions, management strategies, and assessments of function.

RESULTS

Mean age of the participants was 10.22 ± 4.64 years (range, 2.9-19.41). Prevalence rates of orthopedic conditions were as follows: kyphoscoliosis 63.6%, hip displacement 14.6%, knee problems 40%, and foot deformities 75.5%. Significant relationship emerged between spinal (p < 0.01) and knee deformities (p < 0.01) with reduced motor function across various domains. Hip displacement significantly affected sitting ability (p = 0.002), and foot deformities impacted standing and walking capabilities (p = 0.049). Mutation clusters analysis revealed significant correlations with spinal (p = 0.022) and knee deformities (p = 0.002). Linear models highlighted the critical importance of mutation clusters, spine deformities, age, and hip management concerning functional variables.

CONCLUSIONS

In this study, foot deformities were the most frequent orthopedic manifestation, followed by spinal, knee, and hip deformities; and unveiled their relationships with functional status and groups of mutations in RTT patients.

LEVEL OF EVIDENCE

Level IV, Case series.

Case Report of Suspected Gonadal Mosaicism in FOXP1-Related Neurodevelopmental Disorder

Heterozygous mutations in the FOXP1 gene (OMIM#605515) are responsible for a well-characterized neurodevelopmental syndrome known as "intellectual developmental disorder with language impairment with or without autistic features" (OMIM#613670) or FOXP1 syndrome for short. The main features of the condition are global developmental delay/intellectual disability; speech impairment in all individuals, regardless of their level of cognitive abilities; behavioral abnormalities; congenital anomalies, including subtle dysmorphic features; and strabismus, brain, cardiac, and urogenital abnormalities. Here, we present two siblings with a de novo heterozygous FOXP1 variant, namely, a four-year-old boy and 14-month-old girl. Both children have significantly delayed early psychomotor development, hypotonia, and very similar, slightly dysmorphic facial features. A lack of expressive speech was the leading symptom in the case of the four-year-old boy. We performed whole-exome sequencing on the male patient, which identified a pathogenic heterozygous c.1541G>A (p.Arg514His) FOXP1 mutation. His sister's targeted mutation analysis also showed the same heterozygous FOXP1 variant. Segregation analysis revealed the de novo origin of the mutation, suggesting the presence of parental gonadal mosaicism. To the best of our knowledge, this is the first report of gonadal mosaicism in FOXP1-related neurodevelopmental disorders in the medical literature.

Generation of an integration-free induced pluripotent stem cell line, FJMUUHi002-A, from a Rett syndrome patient with a heterozygous mutation p. R133C in MeCP2

The human iPS cell line, hiPS-RTT (FJMUi002-A), is derived from peripheral blood mononuclear cells (PBMCs) from a 12-year-old female RTT patient carrying a heterozygous p. R133C (c.397C > T) mutation in the MeCP2 gene. The hiPS-RTT cell line was generated by non-integrative reprogramming vectors encoding OCT3/4, SOX2, KLF4, and c-MYC and was free of genomically integrated reprogramming genes. The hiPS-RTT cell line had a normal karyotype, expressed pluripotency markers, and had capacity to form three germ layers in vitro and in vivo, which offering a useful resource to study the pathogenesis and treatment strategies of RTT.