Partial DiGeorge syndrome in two patients with a 10p rearrangement

Sperm meiotic segregation of a balanced interchromosomal reciprocal insertion resulting in recurrent spontaneous miscarriage

RESEARCH QUESTION

Is sperm fluorescence in-situ hybridization (FISH) useful to evaluate the risk of chromosomally unbalanced gametes in interchromosomal reciprocal insertion (IRI) carriers? How do these imbalances lead to recurrent miscarriages?

DESIGN

This study reports a clinical and molecular study of a rare familial balanced IRI resulting in recurrent spontaneous miscarriage. Sperm FISH was performed to estimate the number of unbalanced gametes.

RESULTS

A 31-year-old healthy male (proband) and his 28-year-old female partner were referred to the Genetics Department for three spontaneous miscarriages occurring during the first trimester of pregnancy. FISH analysis of the proband with the LSI TRA/D (14q11.2) and DiGeorge N25 (22q11.2) break-apart probes showed the presence of a balanced IRI between 14q11.2 and 22q11.2 chromosomal regions. This IRI was also identified in the proband's father. Sperm FISH with the same probes showed that more than 40% of gametes of the proband were unbalanced for either 14q11.2 or 22q11.2, despite normal sperm parameters. FISH analysis of a product of conception indicated that unbalanced gametes result in a non-viable fetus.

CONCLUSIONS

This study shows the value of sperm FISH analysis in improving genetic reproductive advice for IRI carriers. Disruption of critical genes through this rearrangement and their consequent functional impairment could result in recurrent miscarriages. In this case, several genes located in the 14q11.2 region, particularly RNase 3, would be good candidates to explain the lethality of the imbalances.

Clinical description of a neonate carrying the largest reported deletion involving the 10p15.3p13 region

Chromosome 10p deletion is a rare disorder. This is the largest deletion in chromosome 10p reported to date and the first to be diagnosed in the early neonatal period because of severe clinical manifestations. This rare case might help to understand the genotype‐phenotype spectrum in infants with 10p deletion.

Interstitial 10p deletion derived from a maternal ins(16;10)(q22;p13p15.2): Report of the first familial case of 10p monosomy affecting to two familial members of different generations

Monosomy 10p is a rare chromosomal disorder with a prevalence <1/1,000,000, in which a terminal or interstitial distal region of chromosome 10 is deleted resulting in a variable phenotype depending on the size of the deletion. Two main phenotypes have been defined depending on the location of the deletion: HDR syndrome (Hypoparathyroidism, sensorineural Deafness, and Renal disease), and DGS2 (DiGeorge syndrome type 2). The vast majority of cases reported so far have resulted from de novo events. Here, we present the first familial presentation of this contiguous gene deletion syndrome, affecting two family members in different generations: a child and his maternal uncle. In both cases, the deletion was due to a malsegregation of a maternal balanced rearrangement, ins(16;10)(q22;p13p15.2). The identification and characterization of this rearrangement was possible using a combination of different genetic analyses such as karyotype, MLPA, FISH, and array CGH. We underline the importance of the present results in terms of genetic and reproductive counseling for the carriers of the balanced rearrangement within the family, and demonstrate again the utility of expanding the genetic studies to the relatives of the affected patients.

Osteogenesis imperfecta, tricho-dento-osseous syndrome and intellectual disability: a familial case with 17q21.33-q22 (COL1A1 and DLX3) deletion and 7q32.3-q33 duplication resulting from a reciprocal interchromosomal insertion

We report on a 22-year-old woman with features of osteogenesis imperfecta (OI), tricho-dento-osseous (TDO) syndrome and intellectual disability. Whole genome oligonucleotide microarray analysis revealed a copy number gain of 3 Mb in 7q32.3-q33 and a loss of 3.4 Mb in 17q21.33-q22. FISH analysis showed that the third copy of 7q32 was inserted into the long arm of one chromosome 17, exactly in the region 17q21.33-q22 that was deleted. The maternal uncle presented with clinical features similar to the proposita and had the same chromosomal anomalies. The mother of the proposita and two other family members were balanced carriers of this rearrangement, interpreted as an interchromosomal reciprocal insertion. Reciprocal insertion/four-break rearrangement is a very rare chromosomal event. The deleted region on chromosome 17 contains 39 genes, including COL1A1 and DLX3 involved in OI and TDO syndrome respectively. The CACNA1G gene on the deleted segment of chromosome 17 may be a good candidate gene to explain the intellectual impairment. © 2013 Wiley Periodicals, Inc.

Disorders caused by chromosome abnormalities

Many human genetic disorders result from unbalanced chromosome abnormalities, in which there is a net gain or loss of genetic material. Such imbalances often disrupt large numbers of dosage-sensitive, developmentally important genes and result in specific and complex phenotypes. Alternately, some chromosomal syndromes may be caused by a deletion or duplication of a single gene with pleiotropic effects. Traditionally, chromosome abnormalities were identified by visual inspection of the chromosomes under a microscope. The use of molecular cytogenetic technologies, such as fluorescence in situ hybridization and microarrays, has allowed for the identification of cryptic or submicroscopic imbalances, which are not visible under the light microscope. Microarrays have allowed for the identification of numerous new syndromes through a genotype-first approach in which patients with the same or overlapping genomic alterations are identified and then the phenotypes are described. Because many chromosomal alterations are large and encompass numerous genes, the ascertainment of individuals with overlapping deletions and varying clinical features may allow researchers to narrow the region in which to search for candidate genes.

Diagnosis of cryptic chromosomal syndromes by fluorescence in situ hybridization (FISH)

This unit describes the various methods by which cytogeneticists detect chromosome abnormalities. The unit offers guidance for detecting such abnormalities with fluorescence in situ hybridization (FISH), as well as the benefits, limitations, and other applications of FISH.

Unrelated chromosomal anomalies found in patients with suspected 22q11.2 deletion

Screening for 22q11.2 deletions has not an easy approach due to the wide variability of their associated phenotype. Many clinical features overlap with those of other known syndromes and reported loci. Patients referred to exclude a 22q11.2 deletion are usually tested with a locus-specific FISH probe, with 10% positive cases depending on the selection criteria, but patients testing negative for FISH at 22q11.2 may have other chromosomal aberrations in routine cytogenetic analysis. We tested 819 patients suspected of having a 22q11.2 deletion. Eighty-eight patients (10.7%) were positive for 22q11.2 deletion, whereas 30 patients (3.7%) showed other chromosomal abnormalities involving deletions and duplications, derivative chromosomes, marker chromosomes, apparently balanced and unbalanced translocations and sex chromosome aneuploidies. Of these alterations, 28 did not involve region 22q11 and most had not been associated with 22q11.2 deletion phenotype before. We discuss the similarity of DiGeorge/velocardiofacial syndrome with other known clinical entities and suggest correlations between the new loci and the observed clinical features. The frequency of unrelated chromosomal anomalies reported in this study and in other previous reports highlights the importance of conventional cytogenetic analysis as an initial genome-wide screening tool in all referred patients, and provides useful data to optimize diagnostic and screening protocols according to the most frequent chromosomal findings.

Case of hypoparathyroidism, deafness and renal dysplasia (HDR) syndrome associated with nephrocalcinosis and distal renal tubular acidosis

Hypoparathyroidism, deafness and renal dysplasia (HDR) syndrome is an autosomal dominant disorder characterized by hypoparathyroidism, sensorineural deafness and renal dysplasia. Herein, we report a case of HDR syndrome associated with nephrocalcinosis and distal renal tubular acidosis. A 34-year-old woman was admitted to investigate recurrent stone formation and bilateral nephrocalcinosis. As a 3-year-old child, she had been diagnosed with HDR syndrome without chromosome evaluation. She had spontaneous stone passages on several occasions. On laboratory examination, serum calcium and intact parathyroid hormone at lower levels. Urinary citrate excretion was extremely low at 51.6 mg/day. On an ammonium chloride loading test, complete distal renal tubular acidosis was proved. To prevent the nephrocalcinosis from deteriorating, she was given potassium-sodium citrate. Since administration, she has not experienced spontaneous stone passage or renal colic. Nephrocalcinosis and recurrent urolithiasis will strongly affect renal prognosis in this case and we consider that citrate medication is an effective therapy in avoiding progress of her nephrocalcinosis.

Hypoparathyroidism-retardation-dysmorphism syndrome in a girl: A new variant not caused by aTBCEmutation-clinical report and review

Hypoparathyroidism-retardation-dysmorphism (HRD) or Sanjad-Sakati syndrome (SSS) (OMIM 241410) is a rare autosomal recessive (AR) inherited condition, characterized by congenital hypoparathyroidism (hypoPTH), retardation, seizures, and a typical facial dysmorphism, consisting of prominent forehead, deep-set eyes, and abnormal external ears. This disorder has been mapped to the long arm of chromosome 1 (1q42-q43) and mutations in the gene coding for tubulin-specific chaperone E (TBCE) have been identified as the cause of the disease. Mutations in the same gene were also reported in patients with AR Kenny-Caffey syndrome (KCS). We report on a 41/2-year-old girl with congenital hypoPTH, seizures, developmental delay, and a facial dysmorphism, compatible with HRD syndrome. Mutation analyses revealed no mutations in the TBCE gene. In addition, normal TBCE protein and alpha-tubulin immunostaining were observed in a lymphoblastoid line derived from the patient, excluding the TBCE gene as the causative gene of the syndrome in this patient. A de novo microduplication of probe RP11-262I1 on 4q35 in the proposita was detected by microarray analyses, but this could not be confirmed by additional studies. We review and discuss the clinical findings of our case and those of the other reported cases with SSS and AR KCS. We conclude that a second gene locus for this disorder seems probable and that 4q35 needs further evaluation as a candidate region.

Distinctive collection of fetal anomalies: cleft lip and palate, multicystic dysplastic kidneys, 1-2 syndactyly, heterotopic olivary tissue and thymic hypoplasia

A female fetus with an unusual collection of congenital anomalies was detected prenatally. The pregnancy was terminated at 21 weeks of gestation. Clinical and pathological findings of bilateral cleft lip and palate, micrognathia, thymic hypoplasia, unilateral 1-2 finger syndactyly, bilateral multicystic dysplastic kidneys and heterotopic olivary tissue are presented. Differential diagnoses are discussed.

Small Reciprocal Insertion detected by Spectral Karyotyping (SKY) and delimited by Array-CGH Analysis

A 5.4-year-old male propositus is reported with mild dysmorphic features including hypoplasia of the radial part of both hands affecting thenar, thumb and fingers 2-3, incomplete syndactyly of fingers 3-4, single palmar creases, brachymesophalangia of toes 3-5, dissociated retardation of bone age, telecanthus, spina bifida occulta, cryptorchidism, muscular hypotonia, and borderline mental retardation. His karyotype was unbalanced, 46,XY,der(16)ins(4;16)(q26q28.1; q12.1q12.2)pat. In the propositus' father who had brachydactyly of fingers 2-5 and brachymesophalangia of toes 3-5 the insertion was reciprocal, 46,XY,rep ins(4;16)(q26q28.1;q12.1q12.2). Insertions are rare, reciprocal insertions most unusual. The characterization of the insertion in the propositus and the detection of its reciprocity in the father were achieved by the application of spectral karyotyping (SKY). Further examination of the propositus' unbalanced genome by array-CGH analysis delimited the chromosomal locations of the deletion/insertion rearrangement on a 0.5-2 Mb resolution level and allowed to design specific BAC FISH analyses that pinpointed the borders of the affected segments. The rearrangement involved a segment of 7.7 Mb between RP11-1030 g22 and RP11-52k8 at the chromosomal regions 4q26 and 4q28.1, respectively, and a segment of 2.8 Mb between RP11-242n20 at 16q12.1 and RP11-324d17 at 16q12.2. A simple molecular genetic explanation of the phenotype cannot be given. A relation to the Townes Brocks gene (SALL1) located 340 kb proximal of the 16q12 deletion/insertion is unlikely. Possibly more relevant is an overlap of the 16q12 deletion/insertion with a small deletion of the syntenic chromosomal region in the mouse that causes a developmental disorder of digits ("Fused toes").

GATA-3 in human T cell helper type 2 development

The delineation of the in vivo role of GATA-3 in human T cell differentiation is a critical step in the understanding of molecular mechanisms directing human immune responses. We examined T cell differentiation and T cell–mediated effector functions in individuals lacking one functional GATA-3 allele. CD4 T cells from GATA-3^+/− individuals expressed significantly reduced levels of GATA-3, associated with markedly decreased T helper cell (Th)2 frequencies in vivo and in vitro. Moreover, Th2 cell–mediated effector functions, as assessed by serum levels of Th2-dependent immunoglobulins (Igs; IgG4, IgE), were dramatically decreased, whereas the Th1-dependent IgG1 was elevated compared with GATA-3^+/+ controls. Concordant with these data, silencing of GATA-3 in GATA-3^+/+ CD4 T cells with small interfering RNA significantly reduced Th2 cell differentiation. Moreover, GATA-3 mRNA levels increased under Th2-inducing conditions and decreased under Th1-inducing conditions. Taken together, the data strongly suggest that GATA-3 is an important transcription factor in regulating human Th2 cell differentiation in vivo.

Interstitial deletion of 10p and atrial septal defect in DiGeorge 2 syndrome

We present molecular genetic investigations of a 4-year-old boy with craniofacial dysmorphism and developmental delay. Trivial mitral and tricuspid regurgitation without gross structural abnormality was diagnosed by echocardiography. High-resolution chromosome analysis revealed an interstitial deletion, del(10)(p12.1p12.32). To characterize the deletion size and breakpoints, we performed fluorescence in situ hybridization analysis using 27 BAC clones. Our data demonstrate an approximately 5.5 Mb deletion del(10)(p12.1p12.31). Surprisingly, the BAC clone RP11-56H7 that contains NEBL, an apparent downstream gene of the cardiogenic transcription factor HAND2 previously shown to be deleted in the patients with DiGeorge 2 syndrome and 10p13 deletion, was deleted in our patient with 10p12.1-p12.31 deletion. In addition, we provide clinical data and results of molecular analysis for a patient with multiple congenital anomalies including Ebstein's anomaly, kidney malformations, and 10p13-p14 deletion. We also reviewed 19 patients with congenital heart defects and deletions involving 10p and propose that atrial septal defect (ASD) is a common cardiac anomaly associated with DiGeorge 2 syndrome. Based on genotype-phenotype analysis of published patients and those reported herein, we propose an approximately 1.0 Mb critical region between loci D10S547 and D10S2176 in 10p14 to be associated with ASD. Considering that septal defects are the most frequent congenital heart anomaly, we suggest that further investigations in the 10p critical region are important to identify gene(s) responsible for this common birth defect.

Hearing loss following Gata3 haploinsufficiency is caused by cochlear disorder

Patients with HDR syndrome suffer from hypoparathyroidism, deafness, and renal dysplasia due to a heterozygous deletion of the transcription factor GATA3. Since GATA3 is prominently expressed in both the inner ear and different parts of the auditory nervous system, it is not clear whether the deafness in HDR patients is caused by peripheral and/or central deficits. Therefore, we have created and examined heterozygous Gata3 knockout mice. Auditory brainstem response (ABR) thresholds of alert heterozygous Gata3 mice, analyzed from 1 to 19 months of age, showed a hearing loss of 30 dB compared to wild-type littermates. Neither physiological nor morphological abnormalities were found in the brainstem, cerebral cortex, the outer or the middle ear. In contrast, cochleae of heterozygous Gata3 mice showed significant progressive morphological degeneration starting with the outer hair cells (OHCs) at the apex and ultimately affecting all hair cells and supporting cells in the entire cochlea. Together, these findings indicate that hearing loss following Gata3 haploinsufficiency is peripheral in origin and that this defect is detectable from early postnatal development and maintains through adulthood.

Characterization of GATA3 Mutations in the Hypoparathyroidism, Deafness, and Renal Dysplasia (HDR) Syndrome

The hypoparathyroidism, deafness, and renal dysplasia (HDR) syndrome is an autosomal dominant disorder caused by mutations of the dual zinc finger transcription factor, GATA3. The C-terminal zinc finger (ZnF2) binds DNA, whereas the N-terminal finger (ZnF1) stabilizes this DNA binding and interacts with other zinc finger proteins, such as the Friends of GATA (FOG). We have investigated seven HDR probands and their families for GATA3 abnormalities and have identified two nonsense mutations (Glu-228 --> Stop and Arg-367 --> Stop); two intragenic deletions that result in frameshifts from codons 201 and 355 with premature terminations at codons 205 and 370, respectively; one acceptor splice site mutation that leads to a frameshift from codon 351 and a premature termination at codon 367; and two missense mutations (Cys-318 --> Arg and Asn-320 --> Lys). The functional effects of these mutations, together with a previously reported GATA3 ZnF1 mutation and seven other engineered ZnF1 mutations, were assessed by electrophoretic mobility shift, dissociation, yeast two-hybrid and glutathione S-transferase pull-down assays. Mutations involving GATA3 ZnF2 or adjacent basic amino acids resulted in a loss of DNA binding, but those of ZnF1 either lead to a loss of interaction with specific FOG2 ZnFs or altered DNA-binding affinity. These findings are consistent with the proposed three-dimensional model of ZnF1, which has separate DNA and protein binding surfaces. Thus, our results, which expand the spectrum of HDR-associated GATA3 mutations and report the first acceptor splice site mutation, help to elucidate the molecular mechanisms that alter the function of this zinc finger transcription factor and its role in causing this developmental anomaly.

Perinatal calcium metabolism: physiology and pathophysiology

Disturbances in mineral homeostasis are common in the neonatal period, especially in premature infants and infants who are hospitalised in an intensive care unit. In many cases these disturbances are thought to be exaggerated responses to the normal physiological transition from the intrauterine environment to neonatal independence. By contrast, some disturbances in calcium homeostasis are the result of genetic defects, which in many instances can now be identified at the molecular level. In other cases hypocalcaemia or hypercalcaemia may result from pathological intrauterine conditions, birth trauma or stress, or fetal immaturity. Diagnosis and management of hypocalcaemia and hypercalcaemia in the neonate and infant requires specific knowledge of perinatal mineral physiology and the unique clinical and biochemical features of newborn mineral metabolism. In this chapter we will provide a brief overview of calcium metabolism with an emphasis on the neonatal transition, followed by discussion of the common causes of hypercalcaemia and hypocalcaemia.

22q11.2 deletion syndrome: DiGeorge, velocardiofacial, and conotruncal anomaly face syndromes

A microdeletion of chromosome 22q11.2 is found in most patients with velocardiofacial syndrome, DiGeorge syndrome, and conotruncal anomaly face syndrome, and in some patients with Cayler cardiofacial and autosomal dominant Opitz-G/BBB syndromes. A wide spectrum of clinical findings accompanies the 22q11.2 deletion, without genotype or phenotype correlation even among affected family members. Classic features are dysmorphic facies, conotruncal cardiac defects, hypocalcemic hypoparathyroidism, T-cell mediated immune deficiency, and palate abnormalities. Less well recognized are learning, speech, feeding, and psychiatric disorders, and renal and musculoskeletal defects. Parathyroid and immune deficiencies in the same individual can progress or resolve with time. The 22q11.2 deletion can be inherited as an autosomal dominant or arise as a de novo deletion or translocation. Fluorescent in situ hybridization using cosmid probes mapping to the DiGeorge chromosomal region is a widely available method to detect the 22q11.2 deletion in metaphase chromosomes from cultured lymphocytes, amniocytes, or chorionic villi. The ubiquitin-fusion-degradation-1-like gene, expressed in embryonic branchial arches and in the conotruncus, appears to play a prominent role in the pathogenesis of the 22q11.2 deletion syndrome.

An unusual concurrence of graft versus host disease caused by engraftment of maternal lymphocytes with DiGeorge anomaly

We describe a girl with DiGeorge anomaly and normal cytogenetic and molecular studies, whose clinical course was complicated by graft versus host disease caused by intrauterine materno-fetal transfusion, and several immunohematological alterations including a monoclonal gammapathy of undetermined significance (first IgG, which subsequently changed to IgM). The main clinical features and pathological findings are discussed.

GATA3 haplo-insufficiency causes human HDR syndrome

Terminal deletions of chromosome 10p result in a DiGeorge-like phenotype that includes hypoparathyroidism, heart defects, immune deficiency, deafness and renal malformations. Studies in patients with 10p deletions have defined two non-overlapping regions that contribute to this complex phenotype. These are the DiGeorge critical region II (refs 1, 2), which is located on 10p13-14, and the region for the hypoparathyroidism, sensorineural deafness, renal anomaly (HDR) syndrome (Mendelian Inheritance in Man number 146255), which is located more telomeric (10p14-10pter). We have performed deletion-mapping studies in two HDR patients, and here we define a critical 200-kilobase region which contains the GATA3 gene. This gene belongs to a family of zinc-finger transcription factors that are involved in vertebrate embryonic development. Investigation for GATA3 mutations in three other HDR probands identified one nonsense mutation and two intragenic deletions that predicted a loss of function, as confirmed by absence of DNA binding by the mutant GATA3 protein. These results show that GATA3 is essential in the embryonic development of the parathyroids, auditory system and kidneys, and indicate that other GATA family members may be involved in the aetiology of human malformations.

An HDR (hypoparathyroidism, deafness, renal dysplasia) syndrome locus maps distal to the DiGeorge syndrome region on 10p13/14

Partial monosomy 10p is a rare chromosomal condition and a significant proportion of patients show features of DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS). A critical haploinsufficiency region for DGS/VCFS was defined on 10p (DGCR2). We performed molecular deletion analysis of two further patients with partial monosomy 10p, who showed hypoparathyroidism, deafness, and renal dysplasia or renal insufficiency, but no cardiac defect, cleft palate, or reduced T cell levels. Previously, the combination of hypoparathyroidism, deafness, and renal dysplasia has been proposed to represent a specific syndrome (MIM 146255) under the acronym HDR. In addition to the two patients in this report, at least four published cases with partial monosomy 10p show the triad of HDR and 14 other patients present with at least two of the three features. We therefore conclude that HDR syndrome can be associated with partial monosomy 10p. Based on molecular deletion analysis and the clinical data, we suggest that the DGS/VCFS phenotype associated with 10p deletion can be considered as a contiguous gene syndrome owing to haploinsufficiency of two different regions. Hemizygosity of the proximal region, designated DGCR2, can cause cardiac defect and T cell deficiency. Hemizygosity of the distal region, designated HDR1, can cause hypoparathyroidism and in addition sensorineuronal deafness and renal dysplasia/insufficiency or a subset of this triad.