3M syndrome patient with a novel mutation: A case report

BACKGROUND

A rare autosomal recessive genetic disorder, 3M syndrome, is characterized by severe intrauterine and postnatal growth retardation. Children with 3M syndrome typically exhibit short stature, facial deformities, long tubular bones, and high vertebral bodies but generally lack mental abnormalities or other organ damage. Pathogenic genes associated with 3M syndrome include CUL7, OBSL1 and CCDC8. The clinical and molecular characteristics of patient with 3M syndrome are unique and serve as important diagnostic indicators.

CASE SUMMARY

In this case, the patient displayed square shoulders, scoliosis, long slender tubular bones, and normal neurological development. Notably, the patient did not exhibit the typical dysmorphic facial features, relative macrocephaly, or growth retardation commonly observed in individuals with 3M syndrome. Whole exon sequencing revealed a novel heterozygous c.56681+1G>C (Splice-3) variant and a previously reported nonsense heterozygous c.3341G>A (p.Trp1114Ter) variant of OBSL1. Therefore, it is important to note that the clinical features of 3M syndrome may not always be observable, and genetic confirmation is often required. Additionally, the identification of the c.5683+1G>C variant in OBSL1 is noteworthy because it has not been previously reported in public databases.

CONCLUSION

Our study identified a new variant (c.5683+1G>C) of OBSL1 that contributes to expanding the molecular profile of 3M syndrome.

Chinese patients with 3M syndrome: clinical manifestations and two novel pathogenic variants

Background: 3M syndrome is a rare autosomal recessive disease, characterized by intrauterine and postnatal growth retardation, facial dysmorphism, large head circumference, and skeletal changes, has rarely been reported in the Chinese population. Methods: We describe the clinical manifestations and gene variants in four sporadic cases of 3M syndrome in Chinese individuals from different families. Results: All cases had significant growth retardation, relative macrocephaly, and typical facial features. Exome sequencing revealed that two patients with 3M syndrome had homozygous variants of the CUL7 gene: one novel pathogenic variant and one previously reported pathogenic variant; the other two patients were heterozygous for variants in OBSL1, one of which had not been reported previously. Clinical evaluation indicated that these Chinese patients with 3M syndrome shared similar recognizable features with those reported in patients of other ethnic backgrounds, but not all patients with 3M syndrome in this study had normal development milestones. Two patients underwent recombinant human growth hormone (rhGH) therapy and showed accelerated growth in the first 2 years; however, the growth rate slowed in the third year in one case. There were no obvious adverse reactions during rhGH treatment. Conclusion: We report one novel CUL7 and one novel OBSL1 mutation in patients with 3M syndrome. Children with short stature, specific facial features, and physical symptoms should be referred for genetic testing to obtain precise diagnosis and appropriate treatment. The effects of rhGH treatment on adult height requires long-term observation and study in a large sample.

Natural history of facial and skeletal features from neonatal period to adulthood in a 3M syndrome cohort with biallelic CUL7 or OBSL1 variants

3M syndrome is characterized by severe pre- and post-natal growth restriction, typical face, slender tubular bones, tall vertebral bodies, prominent heels and normal intelligence. It is caused by biallelic variants of CUL7, OBSL1 and, more rarely, CCDC8. The aim of this study is to evaluate facial and skeletal findings in 3M patients from neonatal period to adulthood. A total of 19 patients with a median age of diagnosis of 9.2 months were included in this study and were followed for two to 20 years. CUL7 and OBSL1 variants were found in 57.9% and 42.1% of patients, respectively, five of which are novel. Most of patients had triangular face, frontal bossing, short fleshy nose, full fleshy lower lip, transverse groove of rib cage, hyperlordosis and prominent heels. Three new early-diagnostic signs were observed in infants; two were infraorbital swelling of the lower lid and facial infantile hemangioma, both of which became less pronounced with aging. The third was the central tubercle of the upper lip that became more prominent with in time. While slender long bones did not change with aging, the tall vertebral bodies became more prominent radiologically. The mean birth length in patients was -4.3 SDS. Eight patients reached a mean final height of -4.9 SDS. Despite described growth hormone (GH) insensitivity in 3M syndrome, 12 patients either with GH deficiency or with normal GH levels were treated with GH; seven patients responded with an increase in height SDS. This study not only provided early diagnostic signs of the syndrome, but also presented important follow-up findings.

A rare cause of syndromic short stature: 3M syndrome in three families

3M syndrome is a rare autosomal recessive genetic disorder characterized by severe growth retardation, dysmorphic facial features, skeletal dysplasia, and normal intelligence. Variants in CUL7, OBSL1, and CCDC8 genes have been reported to be responsible for this syndrome. In this study, the clinical and molecular findings of four 3M syndrome cases from three families are presented. All cases had growth retardation, relative macrocephaly, and typical dysmorphic facial features. Their neurological developments were normal. Sequencing of CUL7, OBSL1, and CCDC8 genes revealed two different novel homozygous variants in CUL7 in Families 1 and 3 and a previously reported homozygous pathogenic variant in OBSL1 in Family 2. In conclusion, a comprehensive dysmorphological evaluation should be obtained in individuals presenting with short stature and in such individuals with typical facial and skeletal findings, 3M syndrome should be considered. Our report expands the genotype of 3M syndrome and emphasizes the importance of thorough physical and dysmorphological examination.

The Effect of Combined Growth Hormone and a Gonadotropin-Releasing Hormone Agonist Therapy on Height in Korean 3-M Syndrome Siblings

3-M syndrome is a rare autosomal recessive growth disorder characterized by severe growth retardation, low birth weight, characteristic facial features, and skeletal anomalies, for which three causative genes (CUL7, OBSL1, and CCDC8) have been identified. We herein report two Korean siblings with 3-M syndrome caused by two novel OBSL1 mutations, and describe the effect of a combined treatment with growth hormone (GH) and a gonadotropin-releasing hormone (GnRH) agonist. A 7-year-old girl with short stature (-3.37 standard deviation score, SDS) and breast budding presented with subtle dysmorphic features, including macrocephaly, frontal bossing, a triangular face, prominent philtrum, full lips, a short neck, and fifth-finger clinodactyly. GnRH stimulation test revealed a pubertal pattern and advanced bone age of 8 years and 10 months. Her older sister, aged 10 years and 9 months, had experienced an early menarche, and had an advanced bone age (13.5 years) and predicted adult height of 142 cm (-4.04 SDS). Targeted exome sequencing identified that the siblings had two heteroallelic mutations in OBSL1. Both siblings underwent a combination therapy with GH and a GnRH agonist. A height gain was noted in both siblings even after short-term treatment. To fully elucidate the effects of the combined therapy, a larger cohort should be analyzed following a longer treatment period. However, such an analysis would be challenging due to the rarity of this disease.

Three M syndrome 2 in two Indian patients

3-M syndrome is a rare autosomal recessive disorder, characterized by short stature, characteristic facies and absence of microcephaly and intellectual disability. 3-M syndrome 2 (MIM# 612921) is caused by biallelic disease causing variants in OBSL1. In this study, we identified two probands from two families with homozygous, c.1534 + 5G > T and compound heterozygous variants, c.35dup and c.1273dup in OBSL1, respectively. We herein highlight the clinical and molecular findings of the first reported cases from Indian ethnicity.

HPV caught in the tetraspanin web?

Tetraspanins are master organizers of the cell membrane. Recent evidence suggests that tetraspanins themselves may become crowded by virus particles and that these crowds/aggregates co-internalize with the viral particles. Using microscopy, we studied human papillomavirus (HPV) type 16-dependent aggregates on the cell surface of tetraspanin overexpressing keratinocytes. We find that aggregates are (1) rich in at least two different tetraspanins, (2) three-dimensional architectures extending up to several micrometers into the cell, and (3) decorated intracellularly by filamentous actin. Moreover, in cells not overexpressing tetraspanins, we note that obscurin-like protein 1 (OBSL1), which is thought to be a cytoskeletal adaptor, associates with filamentous actin. We speculate that HPV contact with the cell membrane could trigger the formation of a large tetraspanin web. This web may couple the virus contact site to the intracellular endocytic actin machinery, possibly involving the cytoskeletal adaptor protein OBSL1. Functionally, such a tetraspanin web could serve as a virus entry platform, which is co-internalized with the virus particle.

Further expanding the mutational spectrum and investigation of genotype-phenotype correlation in 3M syndrome

3M syndrome is characterized by severe pre- and postnatal growth retardation, typical facial features, and normal intelligence. Homozygous or compound heterozygous mutations in either CUL7, OBSL1, or CCDC8 have been identified in the etiology so far. Clinical and molecular features of 24 patients (23 patients and a fetus) from 19 unrelated families with a clinical diagnosis of 3M syndrome were evaluated and genotype-phenotype correlations were investigated with the use of DNA sequencing, chromosomal microarray, and whole exome sequencing accordingly. A genetic etiology could be established in 20 patients (n = 20/24, 83%). Eleven distinct CUL7 or OBSL1 mutations, among which eight was novel, were identified in 18 patients (n = 18/24, 75%). Ten patients had CUL7 (n = 10/18, 56%) while eight had OBSL1 (n = 8/18, 44%) mutations. Birth weight and height standard deviation scores at admission were significantly (p < 0.05) lower in patients with CUL7 mutation compared to that of patients with OBSL1 mutation. Two patients with a similar phenotype had a de novo 20p13p deletion involving BMP2. No genetic etiology could be established in four patients (n = 4/28, 17%). This study yet represents the largest cohort of 3M syndrome patients from a single center in Turkey. Microdeletions involving BMP2 may cause a phenotype similar to 3M syndrome with some distinctive features. Larger cohort of patients are required to establish genotype-phenotype correlations in 3M syndrome.

Prenatal and early diagnosis of Chinese 3-M syndrome patients with novel pathogenic variants

BACKGROUND

3-M syndrome is a clinically recognizable yet under-diagnosed primordial growth retardation disorder. Molecular testing for CUL7, OBSL1 or CCDC8 genes can provide confirmed diagnosis for patients at prenatal or early age. So far, the clinical and molecular features of Chinese 3-M syndrome patients have not been reported.

METHODS

In this article, the authors performed prenatal and early diagnosis of Chinese patients with 3-M syndrome by Next-Generation Sequencing.

RESULTS

The authors reported six unrelated Chinese 3-M syndrome patients. Five of the six patients were diagnosed before two years of age including one prenatal case. The authors identified six novel pathogenic variants and five previously reported pathogenic variants. The authors' clinical evaluations indicated that Chinese 3-M syndrome patients share similar recognizable features as those reported in patients of other ethnic background. The authors noticed some uncommon features in this small cohort of Chinese patients such as delayed motor development at early ages, undelayed bone age and presence of lower eyelid fat pads.

CONCLUSION

The authors' study of Chinese 3-M syndrome patients revealed novel mutations and clinical phenotypes.

3-M syndrome: a growth disorder associated with IGF2 silencing

3-M syndrome is an autosomal recessive disorder characterised by pre- and post-natal growth restriction, facial dysmorphism, normal intelligence and radiological features (slender long bones and tall vertebral bodies). It is known to be caused by mutations in the genes encoding cullin 7, obscurin-like 1 and coiled-coil domain containing 8. The mechanisms through which mutations in these genes impair growth are unclear. The aim of this study was to identify novel pathways involved in the growth impairment in 3-M syndrome. RNA was extracted from fibroblast cell lines derived from four 3-M syndrome patients and three control subjects, hybridised to Affymetrix HU 133 plus 2.0 arrays with quantitative real-time PCR used to confirm changes found on microarray. IGF-II protein levels in conditioned cell culture media were measured by ELISA. Of the top 10 downregulated probesets, three represented IGF2 while H19 was identified as the 23rd most upregulated probeset. QRT-PCR confirmed upregulation of H19 (P<0.001) and downregulation of IGF2 (P<0.001). Levels of IGF-II secreted into conditioned cell culture medium were higher for control fibroblasts than those for 3-M fibroblasts (10.2±2.9 vs 0.6±0.9 ng/ml, P<0.01). 3-M syndrome is associated with a gene expression profile of reduced IGF2 expression and increased H19 expression similar to that found in Silver-Russell syndrome. Loss of autocrine IGF-II in the growth plate may be associated with the short stature seen in children with 3-M syndrome.