A recurrent deletion syndrome at chromosome bands 2p11.2-2p12 flanked by segmental duplications at the breakpoints and including REEP1

Expanding Genotype/Phenotype Correlation in 2p11.2-p12 Microdeletion Syndrome

Chromosomal abnormalities on the short arm of chromosome 2 in the region p11.2 have been associated with developmental delay, intellectual disability, facial anomalies, abnormal ears, skeletal and genital malformations. Here we describe a patient with a de novo interstitial heterozygous microdeletion on the short arm of chromosome 2 in the region p11.2-p12. He presents with facial dysmorphism characterized by a broad and low root of the nose and low-set protruding ears. Clinical examinations during follow-up visits revealed congenital pendular nystagmus, decreased visual acuity and psychomotor development disorder including intellectual disability. The heterozygous 5 Mb-microdeletion was characterized by an array CGH (Comparative Genomic Hybridization) analysis. In the past two decades, nine patients with microdeletions in this region have been identified by array CGH analysis and were reported in the literature. All these patients show psychomotor development disorder and outer and/or inner ear anomalies. In addition, most of the patients have mild to severe intellectual disability and show facial malformations. We reviewed the literature on PubMed and OMIM using the gene/loci names as search terms in an attempt to identify correlations between genes located within the heterozygous microdeletion and the clinical phenotype of the patient, in order to define a recognizable phenotype for the 2p11.2p12 microdeletion syndrome. We discuss additional symptoms that are not systematically present in all patients and contribute to a heterogeneous clinical presentation of this microdeletion syndrome.

3q29 microduplication syndrome: Clinical and molecular description of eleven new cases

Interstitial duplications of 3q29 have recently been described in association with a new genetic syndrome characterized by a neurodevelopmental phenotype. A total of 16 individuals with the 3q29 duplication have been reported in the literature with clinical features that include intellectual disability, language delay, epilepsy, structural brain anomalies, micro/macrocephaly, generalized obesity, ocular abnormalities, distinctive facial features, cleft palate, and musculoskeletal anomalies. In this paper, we summarize the current literature and present eleven additional cases from nine families with the 3q29 microduplication identified by microarray analysis at the Cincinnati Children's Hospital Medical Center Laboratory of Genetics and Genomics. Three diagnoses were made prenatally, making this the first case series to describe 3q29 duplications incidentally identified during the prenatal period. We further delineate the minimal region of overlap previously described in the literature and explore the modifying effects of "second hit" genetic aberrations, which were frequent in our cohort.

Screening for REEP1 Mutations in 31 Chinese Hereditary Spastic Paraplegia Families

Background: REEP1 is a common cause of autosomal dominant hereditary spastic paraplegia (HSP) but is rare in China. The pathological mechanism of REEP1 is not fully understood.

Methods: We screened for REEP1 mutations in 31 unrelated probands from Chinese HSP families using next-generation sequencing targeting pathogenic genes for HSP and other related diseases. All variants were validated by Sanger sequencing. The proband family members were also screened for variants for the segregation analysis. All previously reported REEP1 mutations and cases were reviewed to clarify the genetic and clinical features of REEP1-related HSP.

Results: A pathogenic mutation, REEP1c. 125G>A (p.Trp42^*), was detected in a pure HSP family from North China out of 31 HSP families (1/31). This locus, which is located in the second hydrophobic domain of REEP1, is detected in both Caucasian patients with complicated HSP phenotypes and Chinese pure HSP families.

Conclusion: REEP1-related HSP can be found in the Chinese population. The 42nd residue is a novel transethnic mutation hotspot. Mutations in this spot can lead to both complicated and pure form of HSP. Identification of transethnic hotspot will contribute to clarify the underlying pathological mechanisms.

A complete overview of REEP1: old and new insights on its role in hereditary spastic paraplegia and neurodegeneration

At the end of 19th century, Adolf von Strümpell and Sigmund Freud independently described the symptoms of a new pathology now known as hereditary spastic paraplegia (HSP). HSP is part of the group of genetic neurodegenerative diseases usually associated with slow progressive pyramidal syndrome, spasticity, weakness of the lower limbs, and distal-end degeneration of motor neuron long axons. Patients are typically characterized by gait symptoms (with or without other neurological disorders), which can appear both in young and adult ages depending on the different HSP forms. The disease prevalence is at 1.3-9.6 in 100 000 individuals in different areas of the world, making HSP part of the group of rare neurodegenerative diseases. Thus far, there are no specific clinical and paraclinical tests, and DNA analysis is still the only strategy to obtain a certain diagnosis. For these reasons, it is mandatory to extend the knowledge on genetic causes, pathology mechanism, and disease progression to give clinicians more tools to obtain early diagnosis, better therapeutic strategies, and examination tests. This review gives an overview of HSP pathologies and general insights to a specific HSP subtype called spastic paraplegia 31 (SPG31), which rises after mutation of REEP1 gene. In fact, recent findings discovered an interesting endoplasmic reticulum antistress function of REEP1 and a role of this protein in preventing τ accumulation in animal models. For this reason, this work tries to elucidate the main aspects of REEP1, which are described in the literature, to better understand its role in SPG31 HSP and other pathologies.

An intragenic deletion within CTNNA2 intron 7 in a boy with short stature and speech delay: A case report

Background/Objectives:

Deletions on the short arm of chromosome 2 at bands p11 and p12 have been detected in association with short stature, mild mental retardation and speech delay.

Results:

We describe a 4 year-old boy with some facial dysmorphic traits, congenital malformations and pre- and post-natal growth failure. He also presented marked expressive language problems. The molecular karyotype revealed a 108 Kb deletion within the seventh intron of the CTNNA2 gene at 2p11.2-p12. We observed that some features (short stature, facial dysmorphisms and speech delay) were present in our patient and in patients carrying much larger overlapping deletions.

Conclusions:

The description of this small intragenic rearrangement might help to elucidate the role of the single genes included in the 2p11.2-p12 critical region.

Rare interstitial deletion of chromosome 2p11.2p12. Report of a new patient with developmental delay and unusual clinical features

De novo interstitial deletions of the short arm of chromosome 2 are rare chromosomal abnormalities. Patients showing these kind of microdeletions have developmental delay/intellectual disability, minor facial anomalies including high forehead, frontal bossing, broad nasal bridge, abnormal ears and congenital defects such as skeletal and genital malformations. We describe the second child of a healthy and non consanguineous couple presenting at birth multiple malformations and minor facial anomalies. Because of the clinical findings, an array CGH analysis was performed using Agilent 60K microarray oligonucleotide. The analysis detected a 9.3 Mb deletion on the short arm of chromosome 2 at band p11.2p12 spanning the bases 77,946,599-87,277,610. The five patients previously described display a minimal common deleted region which explains the clinical features shared by all of them, while their individual characteristics might be explained by the different sizes of the deletion. The common deleted region involves several genes (CTNNA2, LRRTM1, REEP1), highly expressed in the nervous system. The deletion found in this case overlaps with most of those reported in literature but our patient displays extra clinical signs such as bilateral choanal atresia and atrial septal defect. It was impossible to find any direct correlation between the genes involved in the deletion and the choanal atresia and the heart defect. The question remains open as to whether these clinical features are a consequence of the deletion or are due to a second pathogenic event. Our case emphasizes the difficulties to find a close correlation between a large deletion and a well defined clinical picture. As only five patients with 2p11.2p12 deletions, reported in the literature are characterized by array CGH, further reports will be necessary to well define a clinical phenotype related to the 2p11.2p12 microdeletion.