Genotype-phenotype analysis of 4q deletion syndrome: proposal of a critical region

Chromosome 4q deletion syndrome (4q- syndrome) is a rare condition, with an estimated incidence of 1 in 100,000. Although variable, the clinical spectrum commonly includes craniofacial, developmental, digital, skeletal, and cardiac involvement. Data on the genotype-phenotype correlation within the 4q arm are limited. We present detailed clinical and genetic information by array CGH on 20 patients with 4q deletions. We identified a patient who has a ∼465 kb deletion (186,770,069-187,234,800, hg18 coordinates) in 4q35.1 with all clinical features for 4q deletion syndrome except for developmental delay, suggesting that this is a critical region for this condition and a specific gene responsible for orofacial clefts and congenital heart defects resides in this region. Since the patients with terminal deletions all had cleft palate, our results provide further evidence that a gene associated with clefts is located on the terminal segment of 4q. By comparing and contrasting our patients' genetic information and clinical features, we found significant genotype-phenotype correlations at a single gene level linking specific phenotypes to individual genes. Based on these data, we constructed a hypothetical partial phenotype-genotype map for chromosome 4q which includes BMP3, SEC31A, MAPK10, SPARCL1, DMP1, IBSP, PKD2, GRID2, PITX2, NEUROG2, ANK2, FGF2, HAND2, and DUX4 genes.

2q34-qter duplication and 4q34.2-qter deletion in a patient with developmental delay

The 2q3 duplication and 4q3 deletion syndromes are two conditions with variable phenotypes including Pierre-Robin sequence (PRS), limb anomalies, congenital heart defects (CHD), developmental delays and intellectual disabilities. We describe a patient born to a mother with a balanced t(2; 4) translocation who combines both a 2q34-qter duplication and a 4q34.2-qter deletion through inheritance of the derivative chromosome 4 (der(4)). He showed developmental delay, growth retardation, hearing problems, minor facial and non-facial anomalies, such as bilateral fifth finger shortness and clinodactyly, but no PRS or CHD. The comparison of his features with those of 46 and 65 published cases of 2q3 duplication and 4q3 deletion, respectively, allows us to further restrict the size of the proposed critical intervals for PRS and CHD on chromosome 4.

Novel Vascular Malformation in an Affected Newborn with Deletion Del(4)(q31.3)

We report on a newborn male patient with a terminal deletion in the long arm of the chromosome 4 with a congenital heart defect unreported before in association with this syndrome. The patient had multiple congenital anomalies including a pointed duplicated fingernail, low set posteriorly rotated ears, large anterior fontanel, micrognathia, glabellar capillary vascular malformation, and Interrupted Aortic Arch type C. The patient died due to multiple congenital malformations; a peripheral chromosome analysis showed 46, XY, del(4)(q31.3) de novo. The only reported case with the same deletion was a male newborn that exhibited the pattern of minor anomalies of deletion 4q31 syndrome. The parents were cytogenetically normal. We compare clinical signs to other cases with a deletion in long arm of chromosome 4.

4q34.1-q35.2 deletion in a boy with phenotype resembling 22q11.2 deletion syndrome

Small terminal or interstitial deletions involving bands 4q34 and 4q35 have been described in several patients with a relatively mild phenotype such as mild to moderate intellectual disability and minor dysmorphic features. We present a boy born from unrelated parents with a de novo 4q34.1-q35.2 deletion and clinical features resembling 22q11.2 deletion syndrome. To the best of our knowledge, this is the first reported patient with 4q34-q35 deletion and phenotype resembling 22q11.2 deletion syndrome without fifth finger anomalies as a specific feature of 4q- syndrome. G-banding karyotyping disclosed the deletion, which was further delineated by microarray comparative genomic hybridization. Fluorescence in situ hybridization and multiplex ligation-dependent probe amplification analyses did not reveal rearrangements of 22q11.2 region. MLPA confirmed the deletion within the 4q35.2 region.

CONCLUSION

Given the considerable clinical overlaps between the 22q11.2 deletion syndrome and clinical manifestation of the patient described in this study, we propose that region 4q34.1-q35.2 should be considered as another region associated with phenotype resembling 22q11.2 deletion syndrome. We also propose that distal 4q deletions should be considered in the evaluation of patients with phenotypic manifestations resembling 22q11.2 deletion syndrome in whom no 22q11.2 microdeletion was detected, even in the absence of distinctive fifth finger anomalies. Additionally, we underline the importance of applying array CGH that enables simultaneous genome-wide detection and delineation of copy number changes (e.g., deletions and duplications).

Characterization of an interstitial 4q32 deletion in a patient with mental retardation and a complex chromosome rearrangement

Interstitial deletions of chromosome band 4q32 are rare. We report on a 22-year-old female patient with a de novo interstitial deletion of chromosome 4q32 and a balanced translocation t(2;5)(p21;q12.1). Clinical problems of the patient comprised mild to moderate mental retardation, psychosis, obesity, broad nasal root, sparse lateral eyebrows, thin upper lip, short philtrum, micrognathia, and strabismus. Analysis by whole genome array CGH using an Agilent 244K oligonucleotide array and subsequent FISH using BAC clones from the 4q32 region revealed an unexpectedly complex rearrangement comprising a deletion of approximately 10 Mb in 4q32.1q32.3 and the insertion of two small fragments of 0.8 and 0.11 Mb originating from the derivative chromosome 4q32 into derivative chromosome 5q. The breakpoints of the t(2;5) translocation were mapped by BAC-FISH; no genes were disrupted by these breakpoints. The deleted interval in 4q32 harbored more than 30 genes, and haploinsufficiency of one or several of these genes is likely to have caused the clinical problems of the patient. Candidate genes for cognitive defects are GRIA2, GLRB, NPY1R, and NPY5R. In conclusion, this patient increases our knowledge about the phenotypic consequences of interstitial 4q32 deletions. Reports of patients with overlapping deletions will be needed to elucidate the role of individual genes and to establish genotype-phenotype correlations.

Clinical and genomic characterization of distal duplications and deletions of chromosome 4q: study of two cases and review of the literature

Variable clinical presentations of patients with chromosomally detected deletions in the distal long arm (q) of chromosome 4 have been reported. The lack of molecular characterization of the deletion sizes and deleted genes hinders further genotype-phenotype correlation. Using a validated oligonucleotide array comparative genomic hybridization (oaCGH) analysis, we examined two patients with apparent chromosomal deletions in the distal 4q region. In the first, oaCGH identified a 2.441 megabase (Mb) duplication and a 12.651 Mb deletion at 4q34.1 in a pregnant female who transmitted this aberration to her son. This mother has only learning disabilities while her son had both renal and cardiac anomalies in the newborn period. Unrecognized paternal genetic factors may contribute to the variable expression. The second patient is a 17-year-old female with a history of Pierre Robin sequence, cardiac abnormalities and learning disabilities. She was diagnosed prenatally with a de novo 4q deletion, and oaCGH defined a 16.435 Mb deletion of 4q34.1-4q35.2. Phenotypic comparison and subtractive genomic mapping between these two cases suggested a 4 Mb region possibly harboring a candidate gene for Pierre Robin sequence. Our cases and review of reported cases with genomic findings indicated the presence of familial variants with variable expressivity as well as de novo or inherited pathogenic simple deletion, duplication and complex deletion and duplication in the distal 4q region.

Genetic syndromes involving hearing

OBJECTIVE

The fundamental processes involved in the mechanism of hearing seem to be controlled by hundreds of genes and hereditary hearing impairment may be caused by a large variety of genetic mutations in different genes. Approximately 150 loci for monogenic syndromic and non-syndromic hearing impairment (HI) disorders have been mapped to the human genome. The identification of these genes and functional analysis of the proteins they encode, are paving the way towards a better understanding of the physiology and pathophysiology of the auditory system. To date, approximately 50 causative genes have been identified.

METHODS

The clinical and neuroradioldical findings of syndromal hearing impairment are analysed.

RESULTS

This paper presents an updated report on genetic syndromes in which a hearing impairment is involved, with a particular attention to the ones associated with external ear and craniofacial malformations.

CONCLUSIONS

Concepts in human genetics are rapidly evolving together with technologies. The concept itself of gene is changing. A genetic diagnosis of syndromal hearing impairment has many practical consequences: it can implies specific prognosis, specific management, specific recurrence risk in relatives and, if the diagnosis is confirmed at the molecular level, possibility of a specific early prenatal diagnosis for severe syndromes. It is important to highlight the necessity that the pediatric otolaryngologist must have a close collaboration with a clinical geneticist and a neuroradiologist.