Unrelated Infants Research Articles

Molecular spectrum of SLC22A5 (OCTN2) gene mutations detected in 143 subjects evaluated for systemic carnitine deficiency

Systemic primary carnitine deficiency (CDSP) is caused by recessive mutations in the SLC22A5 (OCTN2) gene encoding the plasmalemmal carnitine transporter and characterized by hypoketotic hypoglycemia, and skeletal and cardiac myopathy. The entire coding regions of the OCTN2 gene were sequenced in 143 unrelated subjects suspected of having CDSP. In 70 unrelated infants evaluated because of abnormal newborn screening (NBS) results, 48 were found to have at least 1 mutation/unclassified missense variant. Twenty-eight of 33 mothers whose infants had abnormal NBS results were found to carry at least 1 mutation/unclassified missense variant, including 11 asymptomatic mothers who had 2 mutations. Therefore, sequencing of the OCTN2 gene is recommended for infants with abnormal NBS results and for their mothers. Conversely, 52 unrelated subjects were tested due to clinical indications other than abnormal NBS and only 14 of them were found to have at least one mutation/unclassified variant. Custom designed oligonucleotide array CGH analysis revealed a heterozygous approximately 1.6 Mb deletion encompassing the entire OCTN2 gene in one subject who was apparently homozygous for the c.680G>A (p.R227H) mutation. Thus, copy number abnormalities at the OCTN2 locus should be considered if by sequencing, an apparently homozygous mutation or only one mutant allele is identified.

Limb malformations with associated congenital constriction rings in two unrelated Egyptian males, one with a disorganization-like spectrum and the other with a probable distinct type of septo-optic dysplasia

In this report, we describe two unrelated Egyptian male infants with limb malformations and constriction rings. The first case is developing normally but has severe limb anomalies, congenital constriction rings, scoliosis because of vertebral anomalies, a left accessory nipple, a small tumor-like swelling on his lower back with tiny skin tubular appendages, a hypoplastic scrotum, and an anchored penis. The second case is developmentally delayed with limb malformations, congenital constriction rings, a lumbar myelomeningeocele, hemangioma, and tiny tubular skin appendages on the back. The patient also had bilateral optic atrophy. The constellation of features in our patients cannot be fully explained by the amniotic disruption complex. The first patient may represent an additional case of the human homolog of the mouse disorganization mutant. The presence of bilateral optic atrophy in the second case, although without an absent septum pellucidum nor other brain anomalies resembles the infrequently reported disorder of septo-optic dysplasia with limb anomalies. Both cases were sporadic and could be caused by a new dominant mutation because of the high paternal age of case 1 and the history of paternal occupational exposure to heat for both fathers. We draw attention to the phenotypic overlap between the disorganization-like syndrome and septo-optic dysplasia with limb anomalies.

Two Infants with Beckwith-Wiedemann Syndrome

Two Infants with Beckwith-Wiedemann SyndromeBeckwith-Wiedemann syndrome (BWS; OMIM 130650) is an overgrowth disorder characterized by macrosomia, macroglossia, organomegaly and developmental abnormalities (in particular abdominal wall defects with exomphalos) and a multi genetic disorder caused by dysregulation of genes expressed in the imprinted 11p15 chromosomal region. We report two unrelated male Moroccan firstborn infants who were hospitalized for macroglossia with breathing difficulties associated with other malformations indicative of BWS.

Chromatic (red/green) and luminance contrast sensitivity in Monozygotic and Dizygotic twin infants

“Purpose: To determine the extent to which contrast sensitivity (CS) development is governed by genetic mechanisms vs. environment, we compared CS between pairs of twin infants and pairs of unrelated infants. If genetics have a strong influence on CS, correlations for Monozygotic (Mz) twin pairs should be greater than those for Dizygotic (Dz) twin pairs, and both Mz and Dz twins should show greater correlations than unrelated infant pairs. By contrast, if genetics have little influence, correlations should be the same for Dz and Mz twins. In this latter scenario, if both Mz and Dz twins show greater correlations than unrelated infant pairs, this suggests a role of shared environment. The current study measured Luminance (light/dark) and Chromatic (red/green) CS to assess sensitivity of the Magnocellular (M) and Parvocellular (P) pathways, respectively. Methods: Nine and 16 pairs of Mz and Dz twin pairs for a total of 50 twin infants were tested (mean age = 5 ±1.5 mos). Zygosity was assessed using a questionnaire and cheek swab kits, when necessary. Luminance and Chromatic CS were obtained using forced-choice preferential looking (˜200 trials per infant; 0.27 cpd; 4.2 Hz; mean luminance = 20 cd/m2). Results: Correlations for both Mz and Dz twins, and for both Luminance and Chromatic CS were significant (all p values 〈 0.002). Monte Carlo simulations on randomly paired unrelated twin infants revealed non-significant correlations (mean r = 0.12 and 0.07 for Luminance and Chromatic), indicating that Mz and Dz twins show greater correlations than unrelated infant pairs, and providing evidence for effects of shared environment. For Luminance CS, the Mz and Dz correlations were nearly identical (rMz = 0.88, rDz = 0.81), suggesting negligible genetic influence. By contrast, for Chromatic CS, the Mz correlation was greater than the Dz correlation (rMz = 0.87; rDz = 0.64), suggestive of a genetic contribution. Multiple regression analyses confirmed that these significant twin effects are not accounted for by small variations in age across infants. Discussion: Results suggest shared environment influences on both Luminance and Chromatic CS, as evidenced by Mz and Dz twins showing greater correlations than unrelated infant pairs. Although more Mz and Dz twins need to be tested, preliminary data suggest less genetic influence on Luminance CS (mediated by the M pathway) than on Chromatic CS (mediated by the P pathway). Future analysis, with more subjects, will employ maximum-likelihood based structural equation modeling (Neale, et al, 2002)”

Acute Infantile Liver Failure Due to Mutations in the TRMU Gene

Acute liver failure in infancy accompanied by lactic acidemia was previously shown to result from mtDNA depletion. We report on 13 unrelated infants who presented with acute liver failure and lactic acidemia with normal mtDNA content. Four died during the acute episodes, and the survivors never had a recurrence. The longest follow-up period was 14 years. Using homozygosity mapping, we identified mutations in the TRMU gene, which encodes a mitochondria-specific tRNA-modifying enzyme, tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase. Accordingly, the 2-thiouridylation levels of the mitochondrial tRNAs were markedly reduced. Given that sulfur is a TRMU substrate and its availability is limited during the neonatal period, we propose that there is a window of time whereby patients with TRMU mutations are at increased risk of developing liver failure.

Mitochondrial mosaics in the liver of 3 infants with mtDNA defects

BackgroundIn muscle cytochrome oxidase (COX) negative fibers (mitochondrial mosaics) have often been visualized.MethodsCOX activity staining of liver for light and electron microscopy, muscle stains, blue native gel electrophoresis and activity assays of respiratory chain proteins, their immunolocalisation, mitochondrial and nuclear DNA analysis.ResultsThree unrelated infants showed a mitochondrial mosaic in the liver after staining for COX activity, i.e. hepatocytes with strongly reactive mitochondria were found adjacent to cells with many negative, or barely reactive, mitochondria. Deficiency was most severe in the patient diagnosed with Pearson syndrome. Ragged-red fibers were absent in muscle biopsies of all patients. Enzyme biochemistry was not diagnostic in muscle, fibroblasts and lymphocytes. Blue native gel electrophoresis of liver tissue, but not of muscle, demonstrated a decreased activity of complex IV; in both muscle and liver subcomplexes of complex V were seen. Immunocytochemistry of complex IV confirmed the mosaic pattern in two livers, but not in fibroblasts. MRI of the brain revealed severe white matter cavitation in the Pearson case, but only slight cortical atrophy in the Alpers-Huttenlocher patient, and a normal image in the 3rd. MtDNA in leucocytes showed a common deletion in 50% of the mtDNA molecules of the Pearson patient. In the patient diagnosed with Alpers-Huttenlocher syndrome, mtDNA was depleted for 60% in muscle. In the 3rd patient muscular and hepatic mtDNA was depleted for more than 70%. Mutations in the nuclear encoded gene of POLG were subsequently found in both the 2nd and 3rd patients.ConclusionHistoenzymatic COX staining of a liver biopsy is fast and yields crucial data about the pathogenesis; it indicates whether mtDNA should be assayed. Each time a mitochondrial disorder is suspected and muscle data are non-diagnostic, a liver biopsy should be recommended. Mosaics are probably more frequent than observed until now. A novel pathogenic mutation in POLG is reported.Tentative explanations for the mitochondrial mosaics are, in one patient, unequal partition of mutated mitochondria during mitoses, and in two others, an interaction between products of several genes required for mtDNA maintenance.

Apnea and bradycardia in two premature infants during routine outpatient retinopathy of prematurity screening

Two unrelated premature infants at risk for retinopathy of prematurity (ROP) were discharged home from a neonatal intensive care unit. Appropriately timed ROP examinations were performed in an outpatient setting in a free-standing pediatric ophthalmologist's private office remote from any hospital. The infants developed severe apnea and bradycardia at the end of the ROP examinations. As a result, a new protocol for outpatient ROP screening was developed.

Contribution of Long-QT Syndrome Genetic Variants in Sudden Infant Death Syndrome

A cohort of 52 French unrelated infant cases who died unexpectedly before they reached 12 months of age was blindly investigated to better quantify the contribution of long-QT syndrome (LQTS) genetic variants in French cases of sudden infant death syndrome (SIDS). After a standardized autopsy protocol, a blinded molecular screening of the KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2 genes was performed on each case. These postmortem investigations enabled us to reclassify 18 as non-SIDS cases, 32 as SIDS cases, and 2 as suspected SIDS cases. Among the 18 non-SIDS cases, no LQTS mutation was identified. In contrast, our results led to a possible explanation for the death of at least three infants in the SIDS cohort. Half of the LQTS gene variants identified were located on the SCN5A gene. This study confirms that LQTS mutations may represent one of the leading genetic causes of SIDS. If autopsy fails to provide an explanation for an unexplained infant death, medicolegal investigation should be extended with a molecular screening of major LQTS genes. Identification of more LQTS mutations in SIDS cases could provide new insights into the pathophysiology of SIDS and, consequently, reduce the number of unexplained sudden infant deaths.

Asymmetries in the individual distinctiveness and maternal recognition of infant contact calls and distress screams in baboons.

A key component of nonhuman primate vocal communication is the production and recognition of clear cues to social identity that function in the management of these species' individualistic social relationships. However, it remains unclear how ubiquitous such identity cues are across call types and age-sex classes and what the underlying vocal production mechanisms responsible might be. This study focused on two structurally distinct call types produced by infant baboons in contexts that place a similar functional premium on communicating clear cues to caller identity: (1) contact calls produced when physically separated from, and attempting to relocate, mothers and (2) distress screams produced when aggressively attacked by other group members. Acoustic analyses and field experiments were conducted to examine individual differentiation in single vocalizations of each type and to test mothers' ability to recognize infant calls. Both call types showed statistically significant individual differentiation, but the magnitude of the differentiation was substantially higher in contact calls. Mothers readily discriminated own-offspring contact calls from those of familiar but unrelated infants, but did not do so when it came to distress screams. Several possible explanations for these asymmetries in call differentiation and recognition are considered.

Agonist-Independent Interactions between β-Arrestins and Mutant Vasopressin Type II Receptors Associated with Nephrogenic Syndrome of Inappropriate Antidiuresis

Nephrogenic syndrome of inappropriate antidiuresis is a recently identified genetic disease first described in two unrelated male infants with severe symptomatic hyponatremia. Despite undetectable arginine vasopressin levels, patients have inappropriately concentrated urine resulting in hyponatremia, hypoosmolality, and natriuresis. It was found that each infant had a different mutation of the vasopressin type II receptor (V2R) at codon 137 where arginine was converted to cysteine or leucine (R137C or R137L), resulting in constitutive signaling. Interestingly, a missense mutation at the same codon, converting arginine to histidine (R137H), leads to the opposite disease phenotype with a loss of the kidney's ability to concentrate urine resulting in nephrogenic diabetes insipidus. This mutation is associated with impaired signaling, although whether this is predominantly due to impaired trafficking to the plasma membrane, agonist-independent internalization, or G protein uncoupling is currently unclear. Using bioluminescence resonance energy transfer and confocal microscopy, we demonstrate that both V2R-R137C and V2R-R137L mutants interact with beta-arrestins in an agonist-independent manner resulting in dynamin-dependent internalization. This phenotype is similar to that observed for V2R-R137H, which is intriguing considering that it is accompanied by constitutive rather than impaired signaling. Consequently, it would seem that agonist-independent internalization per se is unlikely to be the major determinant of impaired V2R-R137H signaling. Our findings indicate that the V2R-R137C and V2R-R137L mutants traffic considerably more efficiently to the plasma membrane than V2R-R137H, identifying this as a potentially important mutation-dependent difference affecting V2R function.

Cross‐sectional and longitudinal association of the secretoglobin 1A1 gene A38G polymorphism with asthma phenotype in the Perth Infant Asthma Follow‐up cohort

Associations between Clara cell secretory protein gene variants (SCGB1A1, also known as CC16, CC10, CCSP and uteroglobin) and the asthma phenotype have been found in five out of eight studies world-wide. No study has investigated the contribution of SCGB1A1 polymorphisms to the development and/or persistence of the asthma phenotype in a birth cohort followed over time. The aim of this study was to determine the role of the SCGB1A1 gene in the development of the asthma phenotype. The Perth Infant Asthma Follow-up (PIAF) cohort (n=231 unrelated infants, unselected for asthma and recruited at birth) were seen at 1 month, 6 and 11 years of age, and had a questionnaire, lung function, airway responsiveness (AR) and skin prick tests (SPTs) completed. Blood was taken at 6 and 11 years for total and specific immunoglobulin E (sIgE) and DNA extraction. SPT positivity had at least one positive SPT. SIgE>4 kU/L had at least one sIgE above 4 kU/L. SCGB1A1 A38G (rs3741240), that alters gene transcription, was genotyped using Sau96I restriction digestion of exon 1 PCR products. At 6 and 11 years of age, 33.0% and 29.7% of those genotyped had doctor-diagnosed asthma, and 35.8% and 52.1% had SPT positivity. In cross-sectional analyses, children with 38G/38A or 38A/38A had increased AR at 1 month (1.72-fold, P=0.013); sIgE>4 kU/L [odds ratio (OR)=6.95, 95% confidence interval (CI)=1.35-35.91, P=0.021]; house dust mite (HDM) SPT positivity (OR=7.21, 95% CI=1.09-47.78, P=0.041) and sIgE (4.57-fold, P=0.045) at 6 years; and doctor-diagnosed asthma (OR=3.93, 95% CI=1.24-12.47, P=0.02) and cat SPT positivity (OR=4.34, 95% CI=1.01-18.77, P=0.049) at 11 years. Longitudinal analyses of 6 and 11 years paired data showed that children with 38A/38A had increased persistent sIgE>4 kU/L (OR=11.87, 95% CI=1.97-71.53, P=0.007) and persistent HDM SPT positivity (OR=7.84, 95% CI=1.04-58.92, P=0.045). SCGB1A1 A38G may play a role in the development and persistence of the asthma phenotype in childhood.

Clinical outcomes in Menkes disease patients with a copper-responsive ATP7A mutation, G727R

Menkes disease is a fatal neurodegenerative disorder of infancy caused by defects in an X-linked copper transport gene, ATP7A. Evidence from a recent clinical trial indicates that favorable response to early treatment of this disorder with copper injections involves mutations that retain some copper transport capacity. In three unrelated infants, we identified the same mutation, G727R, in the second transmembrane segment of ATP7A that complemented a Saccharomyces cerevisiae copper transport mutant, consistent with partial copper transport activity. Quantitative reverse transcription-polymerase chain reaction studies showed approximately normal levels of ATP7A G727R transcript in two patients’ fibroblasts compared to wild-type controls, but Western blot analyses showed markedly reduced quantities of ATP7A, suggesting post-translational degradation. We confirmed the latter by comparing degradation rates of mutant and wild-type ATP7A via cyclohexamide treatment of cultured fibroblasts; half-life of the G727R mutant was 2.9 h and for the wild-type, 11.4 h. We also documented a X-box binding protein 1 splice variant in G727R cells—known to be associated with the cellular misfolded protein response. Patient A, diagnosed 6 months of age, began treatment at 228 days (7.6 months) of age. At his current age (2.5 years), his overall neurodevelopment remains at a 2- to 4-month level. In contrast, patient B and patient C were diagnosed in the neonatal period, began treatment within 25 days of age, and show near normal neurodevelopment at their current ages, 3 years (patient B), and 7 months (patient C). The poor clinical outcome in patient A with the same missense mutation as patient A and patient B with near normal oucomes, confirms the importance of early medical intervention in Menkes disease and highlights the critical potential benefit of newborn screening for this disorder.

Chorioretinal dysplasia, hydranencephaly, and intracranial calcifications: pseudo-TORCH or a new syndrome?

To report the association of severe chorioretinal dysplasia, hydranencephaly, microcephaly, and intracranial calcification in children with no evidence of intrauterine infections. Two unrelated female infants with visually inattentive behaviour, hydranencephaly, and intracranial calcification were referred for an ophthalmological opinion. The fundus examination and computerised tomograms (CT scans) of head were similar in both children. There was bilateral extensive chorioretinal dysplasia, intracranial calcifications, and hydranencephaly. Serology was negative for acquired intrauterine congenital infections. We report two cases that may represent a new syndrome or the more severe end of the spectrum of the pseudo-TORCH (toxoplasma, rubella, cytomegalovirus, and herpes simplex) syndrome. The association of chorioretinal dysplasia with the pseudo-TORCH syndrome has not been reported previously.

Hemorrhagic disease of the newborn despite vitamin K prophylaxis at birth

Late hemorrhagic disease of the newborn (HDN) presents 0.5-6 months after birth with mucocutaneous and intracranial bleeding. We describe here two cases of late HDN in infants who received vitamin K. The first case is a previously healthy breastfed male who received one dose of oral vitamin K at birth and developed an intracranial hemorrhage 5 weeks later. He was treated with intravenous vitamin K and recombinant factor VIIa prior to emergent craniectomy. An unrelated infant presented at 5 months of age with diarrhea and easy bruising despite IM vitamin K at birth. These cases illustrate the morbidity associated with late HDN.

The Role of Environmental Factors in the Causation of Sudden Death in Infants: Two Cases of Sudden Unexpected Death in Two Unrelated Infants Who Were Cared for by the Same Babysitter

We report two cases of sudden unexpected death in two unrelated African American female infants, 2 months and 4 months old. Both infants were attended to by the same babysitter in the same apartment and died 39 days apart in the same bed and in the same bedroom. The autopsy of the first infant revealed sudden unexplained death in an infant. Toxicologic analysis for carbon monoxide (CO) was not performed because it was not suspected. When the second infant died, investigation into the ambient air quality within the apartment revealed high levels of CO emanating from a poorly ventilated and defective hot water heater, which was located across a hallway from the bedroom where the two babies died. CO saturation levels in the postmortem blood samples of the two babies were elevated and were similar (13% and 14%). Nicotine and cotinine were not detected in the blood sample of the two infants. Cherry-red livor mortis was absent. Acute CO intoxication was determined to be the underlying cause of these two unexpected deaths. These two cases underscore the need to integrate ambient air analysis and postmortem CO analysis as routine components of the comprehensive death investigation of infants who die suddenly and unexpectedly.

Behavior, Ecology, and Conservation of Colobine Monkeys: An Introduction

The Colobinae of Africa and Asia are perhaps best known for their specialized stomachs, which allow them to subsist on leafier and more chemically defended diets than most other primates (Kay and Davies, 1994; Oates et al., 1994). Many colobines are also renowned for their shy and indolent dispositions (Fashing, 2006), traits that make them particularly challenging study subjects. Nevertheless, research on colobines has led to some of the most exciting and contentious discoveries in the history of primate behavior and ecology. Over the past 3 decades, colobines have been at the center of an ongoing debate about the adaptive function of infant killing by males. After repeatedly witnessing male Hanuman langurs (Semnopithecus entellus) attempting to kill unrelated infants on Mount Abu, India in the early 1970s, Hrdy (1974, 1977) proposed the groundbreaking hypothesis that infanticide was part of a sexually selected alternative male reproductive strategy. In addition to inspiring a legion of impassioned detractors (Bartlett et al., 1993; Curtin and Dolhinow, 1979), Hrdy’s hypothesis stimulated a large body of research not only on primates, but also on other animals, from burying beetles to barn swallows to lions (van Schaik and Janson, 2000). Though the issue of infanticide’s adaptive function for male primates remains far from resolved today, at present the strongest evidence consistent with the

Novel mutations in the gene encoding ATP binding cassette protein member A3 (ABCA3) resulting in fatal neonatal lung disease

To investigate whether intractable respiratory distress syndrome in three Norwegian term infants was due to mutations in the ABCA3 gene. The genes encoding SP-B (SFTPB), SP-C (SFTPC), and ABCA3 (ABCA3) were sequenced from the parents of one infant and two unrelated infants with fatal neonatal lung disease. Lung tissue was examined by histology, immunohistochemistry and electron microscopy. Novel ABCA3 mutations were identified in each family. One patient had a phenotype differing from previous descriptions of this disease with an initial uneventful period. The diagnosis was established 19 years after death by analysing DNA material from the parents, with an ABCA3 mutation identified on one allele in each parent. The other two infants had more typical clinical courses with the onset of respiratory symptoms immediately after birth. ABCA3 mutations were identified on both alleles from these two infants, and electron microscopy of alveolar type 2 cells demonstrated abnormal lamellar body formation characteristic of this disorder. ABCA3 mutations were the basis for lung disease in all three patients. Children with lung disease due to ABCA3 deficiency may not have symptoms at birth. The finding of five novel mutations indicates allelic heterogeneity for ABCA3 mutations within the Norwegian population.

Nephrogenic Syndrome of Inappropriate Antidiuresis: A Novel Disorder in Water Balance in Pediatric Patients

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia. We report findings in 2 unrelated male infants whose clinical presentation and laboratory findings were consistent with SIADH, but who exhibited unmeasurable arginine vasopressin (AVP) levels on repeated occasions. We hypothesized that these infants had a novel gain of function defect in the AVP-signaling pathway. DNA sequencing of each patient’s vasopressin V 2 receptor (V 2R) gene identified mutations (R137C or R137L) in each. R137H mutations have been reported previously to cause nephrogenic diabetes insipidus. To further characterize the effects of these mutations, we re-created each mutation by site-directed mutagenesis in a vasopressin V 2R expression vector and cotransfected COS-7 cells with wild-type and mutant vasopressin V 2R vectors and a cyclic adenosine monophosphate–responsive luciferase reporter plasmid. The luciferase activity was induced 7.5-fold (R137L mutant; P = 0.0037) and 4-fold (R137C mutant; P = 0.013) more than the wild-type vasopressin V 2R, which is the empty vector or the inactivating R137H mutant. This novel gain of function mutation in the vasopressin V 2R can cause constitutive activation of the receptor and resultant hyponatremia. These findings represent a previously unrecognized genetic disease, which was designated as nephrogenic syndrome of inappropriate antidiuresis. A number of questions have emerged, including the following: (1) What is the frequency? (2) Are there nonrenal manifestations? (3) Are heterozygotes affected? (4) What is the optimal therapy? and (5) How do these mutations cause constitutive activation of the receptor?

Hyponatraemia for the clinical endocrinologist

Hyponatraemia for the clinical endocrinologist

Síndrome de Aicardi-Goutières: aportación de dos nuevas observaciones

Aicardi-Goutières syndrome is an early onset autosomal recessive progressive encephalopathy, clinically characterized by acquired microcephaly, severe psychomotor delay and involvement of pyramidal and extrapyramidal tracts. Intracranial calcifications, especially at the level of the basal ganglia, white matter abnormalities, lymphocytosis and raised interferon (IFN)-alpha in blood and cerebrospinal fluid (CSF) form part of this syndrome. We describe two unrelated infants (a 3-month-old boy and an 11-month-old girl) who both presented with hypotonia, microcephaly, and psychomotor delay. Mild choreic and dystonic movements, as well as progressive spasticity, were also observed in the girl. Extensive investigations revealed intracranial calcifications, mild CSF lymphocytosis in the boy, and raised IFN-a in blood and CSF in both patients. Aicardi-Goutières syndrome should be kept in mind when investigating microcephalic and retarded patients with cerebral calcifications initially suggestive of TORCH infection. Appropriate genetic counseling should be provided.