A mutational hotspot in AMOTL1 defines a new syndrome of orofacial clefting, cardiac anomalies, and tall stature

AMOTL1 encodes angiomotin-like protein 1, an actin-binding protein that regulates cell polarity, adhesion, and migration. The role of AMOTL1 in human disease is equivocal. We report a large cohort of individuals harboring heterozygous AMOTL1 variants and define a core phenotype of orofacial clefting, congenital heart disease, tall stature, auricular anomalies, and gastrointestinal manifestations in individuals with variants in AMOTL1 affecting amino acids 157-161, a functionally undefined but highly conserved region. Three individuals with AMOTL1 variants outside this region are also described who had variable presentations with orofacial clefting and multi-organ disease. Our case cohort suggests that heterozygous missense variants in AMOTL1, most commonly affecting amino acid residues 157-161, define a new orofacial clefting syndrome, and indicates an important functional role for this undefined region.

Estrogen-related receptor gamma implicated in a phenotype including hearing loss and mild developmental delay

Analysis of chromosomal rearrangements has been highly successful in identifying genes involved in many congenital abnormalities including hearing loss. Herein, we report a subject, designated DGAP242, with congenital hearing loss (HL) and a de novo balanced translocation 46,XX,t(1;5)(q32;q15)dn. Using multiple next-generation sequencing techniques, we obtained high resolution of the breakpoints. This revealed disruption of the orphan receptor ESRRG on chromosome 1, which is differentially expressed in inner ear hair cells and has previously been implicated in HL, and disruption of KIAA0825 on chromosome 5. Given the translocation breakpoints and supporting literature, disruption of ESRRG is the most likely cause for DGAP242's phenotype and implicates ESRRG in a monogenic form of congenital HL, although a putative contributory role for KIAA0825 in the subject's disorder cannot be excluded.

A novel duplication in the FMR1 gene: implications for molecular analysis in fragile X syndrome and repeat instability

We have observed a 49 bp tandem duplication adjacent to the triplet repeat of the FMR1 gene and have shown it to occur as a variant in Finland. It affects the primers commonly used in molecular analysis of fragile X syndrome by polymerase chain reaction (PCR) methods. One concern is that females with the full mutation and variant alleles might be missed because of the two PCR products generated by the variant. We suggest that the duplication has arisen by a misalignment of the proximal end of the repeat tract and the non-adjacent GGCGGCGGCGG-sequence located 37 bp upstream and may indicate a mutation hot spot. The discovery of this duplication and the previous observations on deletions associated with full mutations in FMR1 indicate that realignment between the repeat tract and dispersed non-adjacent homologous repetitive sequences may also play a role in repeat instability in fragile X.

More severe epilepsy and cognitive impairment in the offspring of a mother with mosaicism for the ring 20 chromosome

PURPOSE

Ring chromosome 20 [r(20)] syndrome is a rare chromosomal disorder. Cases tend to be sporadic. We elucidate the characteristics of an inherited r(20) mosaicism by describing the clinical features of three family members: a mother and her two children.

RESULTS

The mosaicism rate of the mother was 10% and that of the children 40%. The mother experienced her first epileptic seizures at 24 years of age. Epilepsy was diagnosed two years later. After an unstable period lasting 3 years, she has been seizure-free for 13 years on a combination of valproate and lamotrigine. She has normal intelligence with full working capacity. The daughter exhibited her first epileptic seizures at the age of 7 years and she continues to have seizures weekly. The first epileptic seizures in the son were observed at 5 years of age. The son's epilepsy has been drug resistant from the onset, and a vagal nerve stimulator (VNS) has been ineffective. Psychomotor development was normal in both children up to the onset of epilepsy. Learning difficulties increased throughout school age and both children needed special educational programs. Neuropsychological evaluations have shown deterioration of cognitive levels. Both children had behavioural problems during school age but no longer in adolescence. All three subjects are nondysmophic, normocephalic and of normal growth.

CONCLUSION

In this family the phenotype of r(20) mosaicism seems to be more severe in the successive generation along with a greater level of mosaicism. The aggravated clinical picture in inherited r(20) mosaicism concerned the onset of epilepsy, drug responsiveness, the cognitive level and behavioural features.

Mutations in SEPT9 cause hereditary neuralgic amyotrophy

Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant recurrent neuropathy affecting the brachial plexus. HNA is triggered by environmental factors such as infection or parturition. We report three mutations in the gene septin 9 (SEPT9) in six families with HNA linked to chromosome 17q25. HNA is the first monogenetic disease caused by mutations in a gene of the septin family. Septins are implicated in formation of the cytoskeleton, cell division and tumorigenesis.

New options for prenatal diagnosis in autosomal recessive polycystic kidney disease by mutation analysis of the PKHD1 gene

Due to the poor prognosis of severe autosomal recessive polycystic kidney disease (ARPKD), there is a strong demand for prenatal diagnosis (PD). Reliable PD testing is possible by molecular genetic analysis only. Although haplotype-based analysis is feasible in most cases, it is associated with a risk of misdiagnosis in families without pathoanatomically proven diagnosis. Linkage analysis is impossible in families where DNA of the index patient is not available. Direct mutation analysis of the recently identified polycystic kidney and hepatic disease 1 gene opens new options in families to whom a reliable PD cannot be offered on the basis of linkage analysis. We for the first time report two cases with PD based on mutation detection, illustrating the new options for PD in ARPKD.

Diagnosis and treatment of a newborn with homozygous protein C deficiency

The case is reported of a seriously affected newborn with homozygous protein C deficiency who developed neonatal purpura fulminans. Foetal ultrasound at 33 wk of gestation revealed ventriculomegaly. The first lesions appeared on the scalp 48 h after birth. She was initially treated with fresh-frozen plasma and, after the diagnosis was confirmed, with purified protein C concentrate. After skin necrosis had healed, therapy was continued with oral warfarin. The infant was homozygous for protein C W380G mutation. Diagnosis at the DNA level gave the parents an option of reliable prenatal diagnosis in their subsequent pregnancy.

CONCLUSION

Difficulties in reaching an accurate diagnosis are discussed since early diagnosis and urgent therapy with protein C replacement are crucial to avoid further damage after delivery.

Risk of obstetric cholestasis in sisters of index patients

The aim of the present study was to evaluate the rate of intrahepatic cholestasis of pregnancy in first-degree relatives of index patients. Index patients (n=65) with singleton pregnancies complicated by intrahepatic cholestasis were identified among the women (n=11 984) who gave birth at Kuopio University Hospital in 1994-1998. The pregnancy histories of relatives of 56 index patients were reviewed and the rate of cholestasis in first-degree relatives was compared with that in the general obstetric population. Obstetric cholestasis was experienced by 9% of the parous sisters and 11% of the mothers of the index patients. The risk per delivery was 6% in the first-degree relatives. The rate in the general obstetric population was 0.54%. The odds ratios and 95% confidence intervals were 12.6 (5.6-28.1) for the sisters and 12.2 (6.2-24.2) for the mothers. Obstetric cholestasis clusters within some families and is under strong genetic influence, although the precise genetic pattern remains obscure. The sisters of index patients are at an increased risk of the disorder and may benefit from close obstetric care.

A population-based study on epilepsy in mentally retarded children

PURPOSE

This study presents data on cumulative risk of seizures, cause, comorbidity, and remission of epilepsy among mentally retarded (MR) children followed until the age of 22 years.

METHODS

A total of 151 MR children were identified at the age of 8 or 9 years by screening four birth cohorts of 12,882 children born from 1969 to 1972 in the Finnish province of Kuopio. Information about epilepsy was gathered longitudinally when children were 9 to 10, 17, and 22 years old. The guidelines for epidemiological studies on epilepsy proposed by the International League Against Epilepsy were followed.

RESULTS

By the age of 10 years, 29 of the 151 MR children (19%) had epilepsy. The cumulative risk for epilepsy at 22 years was 21%. The probability of developing epilepsy was increased fivefold in severely MR children compared with mildly MR children, i.e., in 27 of the 77 severely MR children (35%) versus 5 of the 74 mildly MR children (7%). Postnatal causes of mental retardation or association with cerebral palsy increased the risk for epilepsy, especially in the mildly MR children. When these risk factors were not present, the mildly MR children exhibited only a 3% risk for epilepsy, whereas the respective risk was about 10-fold in severe mental retardation. The cumulative probability of epilepsy being in remission for 5 years by the age of 22 was 32%.

CONCLUSIONS

The cumulative risk of epilepsy varies according to the severity and the cause of the retardation as well as the presence of additional disabilities. The cumulative probability of epilepsy remission tended to increase with age.

Molecular diagnosis of medium-chain acyl-CoA dehydrogenase deficiency by oligonucleotide ligation assay

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a recessively inherited defect in the mitochondrial β-oxidation of fatty acids. A single nucleotide change, the A985→G transition, in the MCAD gene accounts for ∼90% of all the disease-causing mutations in the patients. We have used PCR to amplify a segment of the human MCAD gene and typed the allelic sequence variation at base 985 by a colorimetric oligonucleotide ligation assay (OLA). PCR/OLA provides a technique that permits differentiation of the homozygotes, heterozygotes, and normals for the A985→G allele in the MCAD gene. Genotyping of 1908 random Finnish DNA samples by OLA identified 10 carriers of the mutant allele, but no homozygotes were found. The calculated carrier frequency for the A985→G mutation was 1:191 (95% confidence limits, 1:118–1:501), and the calculated frequency for the A985→G homozygotes was 1:147 000 (95% confidence limits, 1:56 000–1:1 004 000).

Molecular diagnosis of medium-chain acyl-CoA dehydrogenase deficiency by oligonucleotide ligation assay

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a recessively inherited defect in the mitochondrial beta-oxidation of fatty acids. A single nucleotide change, the A985 --> G transition, in the MCAD gene accounts for approximately 90% of all the disease-causing mutations in the patients. We have used PCR to amplify a segment of the human MCAD gene and typed the allelic sequence variation at base 985 by a colorimetric oligonucleotide ligation assay (OLA). PCR/OLA provides a technique that permits differentiation of the homozygotes, heterozygotes, and normals for the A985 --> G allele in the MCAD gene. Genotyping of 1908 random Finnish DNA samples by OLA identified 10 carriers of the mutant allele, but no homozygotes were found. The calculated carrier frequency for the A985 --> G mutation was 1:191 (95% confidence limits, 1:118-1:501), and the calculated frequency for the A985 --> G homozygotes was 1:147,000 (95% confidence limits, 1:56,000-1:1,004,000).

The effect of intraoperative injection of hyaluronan under a one-piece glaucoma filtration implant in the rabbit eye

The effect of a single intraoperative injection of hyaluronan on intraocular pressure (IOP) and postsurgical tissue healing was evaluated on 18 rabbits with an aqueous drainage implant. During the follow-up period IOP was recorded and analysed. Furthermore, inflammatory reaction and appearance of the fibrous tissue around the implants were studied in histological sections. In both the hyaluronan and control groups the operation lowered the average IOP statistically significantly for the whole follow-up period when compared with preoperative values. From days 7 to 60 the mean IOP values of the hyaluronan injected eyes stayed at a lower level than in the control eyes, but with no statistical difference between the 2 groups. The connective tissue layer around the implants appeared less dense during the first 17 postoperative days in the sodium-hyaluronate group; in addition, the inflammatory cell reaction showed a tendency to remain acute longer.

Instrumented measurement of anterior-posterior translation in knees with chronic anterior cruciate ligament tear

Anteroposterior translation of the knee joint was measured with a Knee Signature System device on 12 women and 14 men with a unilateral, chronic, isolated, anterior cruciate ligament (ACL) tear. A control group with stable knees consisted of 10 women and 10 men. Anterior translation at 178 N load of the uninjured knees was 8.0 mm (+/-2.2 mm) and in knees with an ACL tear, 14.2 mm (+/-4.2 mm). Corresponding values for anteroposterior translation were 12.1 mm (+/-2.5 mm) and 19.3 mm (+/-4.9 mm), respectively. A difference of 3 mm or more in anteroposterior translation at 178 N load between injured and uninjured knees indicated an ACL tear with 85% specificity and 88% sensitivity.

The effect of intraoperative injection of hyaluronan under a one-piece glaucoma filtration implant in the rabbit eye

The effect of a single intraoperative injection of hyaluronan on intraocular pressure (IOP) and postsurgical tissue healing was evaluated on 18 rabbits with an aqueous drainage implant. During the follow-up period IOP was recorded and analysed. Furthermore, inflammatory reaction and appearance of the fibrous tissue around the implants were studied in histological sections. In both the hyaluronan and control groups the operation lowered the average IOP statistically significantly for the whole follow-up period when compared with preoperative values. From days 7 to 60 the mean IOP values of the hyaluronan injected eyes stayed at a lower level than in the control eyes, but with no statistical difference between the 2 groups. The connective tissue layer around the implants appeared less dense during the first 17 postoperative days in the sodium-hyaluronate group; in addition, the inflammatory cell reaction showed a tendency to remain acute longer.

A population-based study on the causes of mild and severe mental retardation

The causes of mental retardation (MR) were studied as part of a multidisciplinary epidemiological case-control study in 151 mentally retarded patients identified by screening four age cohorts (12,882 children) at 8-9 years of age in the province of Kuopio, Finland. The causes of MR in 77 severely retarded (SD < or = -3 SD) and 74 mildly retarded (-2 > SD > -3) children were divided into pre-, peri-, postnatal and unknown groups according to the probable time of onset. The causes were pre-, peri-, postnatal and unknown in 60%, 9%, 8% and 23%, and 22%, 1%, 3% and 74%, in the two populations, respectively. Genetic causes were found in 28% of all 151 cases; the three most common subgroups were trisomy 21, fragile X syndrome and aspartylglycosaminuria (13%, 4% and 2% respectively). The study design used provided reliable information on the causes of MR and also demonstrated those forms of genetic metabolic diseases typical of Finnish inheritance.

Enzymatic diagnosis of aspartylglycosaminuria by fluorometric assay of glycosylasparaginase in serum, plasma, or lymphocytes

Serum, plasma, and lymphocytes from aspartylglycosaminuria (AGU) patients and carriers and from normal controls were incubated with a fluorescent glycosylasparaginase substrate, L-aspartic acid beta-(7-amido-4-methylcoumarin), and the release of 7-amino-4-methylcoumarin was measured fluorometrically after incubation for 1-4 h. The mean glycosylasparaginase (EC 3.5.1.26) activity in normal serum, plasma, and lymphocytes was 20.2 (SD 5.0) mU/L (n = 24), 17.5 (SD 5.0) mU/L (n = 24), and 242 (SD 108) mU/g protein (n = 17), respectively. The corresponding values in the Finnish AGU patients were 0.7 (SD 0.4) mU/L (n = 10), 0.3 (SD 0.3) mU/L (n = 10), and 6.0 (SD 4.6) mU/g protein (n = 7). No overlapping values were obtained between the AGU patients and the carriers in any of the samples, but the values between the carriers and controls were overlapping in 28 of 29 serum, 22 of 29 plasma, and 4 of 21 lymphocyte samples. Thus, the fluorometric glycosylasparaginase assay in various blood samples allows specific detection of the enzyme defect in AGU, but cannot be used for reliable detection of carriers of the disease.

Enzymatic diagnosis of aspartylglycosaminuria by fluorometric assay of glycosylasparaginase in serum, plasma, or lymphocytes

Serum, plasma, and lymphocytes from aspartylglycosaminuria (AGU) patients and carriers and from normal controls were incubated with a fluorescent glycosylasparaginase substrate, L-aspartic acid beta-(7-amido-4-methylcoumarin), and the release of 7-amino-4-methylcoumarin was measured fluorometrically after incubation for 1-4 h. The mean glycosylasparaginase (EC 3.5.1.26) activity in normal serum, plasma, and lymphocytes was 20.2 (SD 5.0) mU/L (n = 24), 17.5 (SD 5.0) mU/L (n = 24), and 242 (SD 108) mU/g protein (n = 17), respectively. The corresponding values in the Finnish AGU patients were 0.7 (SD 0.4) mU/L (n = 10), 0.3 (SD 0.3) mU/L (n = 10), and 6.0 (SD 4.6) mU/g protein (n = 7). No overlapping values were obtained between the AGU patients and the carriers in any of the samples, but the values between the carriers and controls were overlapping in 28 of 29 serum, 22 of 29 plasma, and 4 of 21 lymphocyte samples. Thus, the fluorometric glycosylasparaginase assay in various blood samples allows specific detection of the enzyme defect in AGU, but cannot be used for reliable detection of carriers of the disease.

Substrate specificity and reaction mechanism of human glycoasparaginase. The N-glycosidic linkage of various glycoasparagines is cleaved through a reaction mechanism similar to L-asparaginase

Human glycoasparaginase (N4-(beta-N-acetyl-D-glucosaminyl)-L-asparaginase, EC 3.5.1.26) hydrolyzes a series of compounds that contain L-asparagine residue with free alpha-amino and alpha-carboxyl groups. Substrates include high mannose and complex type glycoasparagines as well as those that lack the di-N-acetylchitobiose moiety, L-aspartic acid beta-methyl ester and L-aspartic acid beta-hydroxamate. The enzyme is inactive toward L-asparagine and L-glutamine and glycoasparagines containing substituted alpha-amino and/or alpha-carboxyl groups. In the presence of the acyl acceptor hydroxylamine, glycoasparaginase catalyzes the synthesis of L-aspartic acid beta-hydroxamate from aspartyl-glucosamine, L-aspartic acid beta-methyl ester, and L-aspartic acid. 13C NMR studies using 18O-labeled L-aspartic acid demonstrate that glycoasparaginase catalyzes an oxygen exchange between water and the carboxyl group at C-4 of L-aspartic acid. These results indicate that glycoasparaginase reacts as an exo-hydrolase toward the L-asparagine moiety of the substrates and the free alpha-amino and alpha-carboxyl groups are required for the enzyme reaction. The results are consistent with an L-asparaginase-like reaction pathway which involves a beta-aspartyl enzyme intermediate. Since glycoasparaginase is active toward a series of structurally different glycoasparagines, we suggest the revised systematic name of N4-(beta-glycosyl)-L-asparaginase for the enzyme.

Aspartylglycosaminuria in a non-Finnish patient caused by a donor splice mutation in the glycoasparaginase gene

Aspartylglycosaminuria is a lysosomal storage disease caused by deficient activity of glycoasparaginase (EC 3.5.1.26), and it occurs with a high frequency among Finns. We have recently shown that the molecular defect in all Finnish aspartylglycosaminuria patients examined to date consists of two single base changes in the heavy chain of glycoasparaginase (Mononen, I., Heisterkamp, N., Kaartinen, V., Williams, J. C., Yates, J. R., III, Griffin, P. R., Hood, L. E., and Groffen, J. (1991) Proc. Natl. Acad. Sci U.S.A. 88, 2941-2945). This is the first report on the identification of the molecular defect causing aspartylglycosaminuria in a patient of non-Finnish origin. Total RNA from fibroblasts of a black American aspartylglycosaminuria patient was isolated, first-strand cDNA was synthesized, and the cDNA encoding glycoasparaginase was amplified by the polymerase chain reaction. The patient's mRNA nucleotide sequence was different from the normal sequence by a deletion of 134 nucleotides at positions 807-940. Nucleotide sequence analysis of the normal glycoasparaginase gene demonstrated that the deletion corresponded precisely to a 134-base pair exon. Moreover, analysis of the splice sites demonstrated a single base change, G to T, that altered the donor splice site of the exon deleted in the patient's mRNA. This change led to an exon-skipping event resulting in a frame shift and generation of a stop codon.

A one-piece ocular drainage implant for glaucoma surgery: a preliminary report

A one-piece silicone filtration implant for glaucoma surgery was evaluated in 18 normotensive rabbits. During the follow-up period of 60 days the function of the implant and the effect of the implant on intraocular pressure (IOP) and local reaction in operated eyes were examined. Mean IOP in operated eyes during the whole follow-up period stayed in a level that was statistically significantly (p < 0.001) lower than the preoperative starting value. Despite of a slight inflammatory reaction in the immediate postoperative period the implants were well tolerated. No marked foreign body reaction were noted around the implants in histological sections. In 3 eyes the implants had to be removed due to complications caused by surgical technique.

High prevalence of aspartylglycosaminuria among school-age children in eastern Finland

A high prevalence of the lysosomal storage disease aspartylglycosaminuria was found in a study of four birth cohorts of 12882 children in eastern Finland. Using school achievement tests and registers of mentally retarded individuals, 178 mentally retarded children were identified. Randomized urine samples from 151 of the 178 retarded children and from 101 healthy children were analyzed quantitatively for aspartylglucosamine by high-performance liquid chromatography. The results identified three affected individuals in the retarded group indicating an exceptionally high prevalence of aspartylglycosaminuria (1:3643) in the study population, consistent with a carrier frequency of 1:30. The 95% confidence limits for the prevalence are 1:4 352-1:16389. This is the highest prevalence described for any glycoproteinosis in any population and comparable to the incidence figures of the most common lysosomal storage diseases, Gaucher disease type I and Tay-Sachs disease among Ashkenazi Jews. In the study group, aspartylglycosaminuria was, after trisomy 21 (n = 19) and the fragile X syndrome (n = 6), the most common genetic cause for mental retardation.

Amniotic fluid glycoasparagines in fetal aspartylglycosaminuria

Midterm amniotic fluid samples from one pregnancy with the fetus affected by aspartylglycosaminuria and from 11 normal pregnancies were analysed for glycoasparagines accumulating in urine in aspartylglycosaminuria. The aspartylglucosamine concentration in the affected pregnancy was about five times higher than in the controls, but the absolute value was very low being only about one-thousandth of that in urine in aspartylglycosaminuria and one-tenth of that in urine samples from normal adults. In total monosaccharide analysis, only galactose content in the affected amniotic fluid was slightly elevated compared to controls, indicating that higher glycoasparagines typical of urine in aspartylglycosaminuria were not accumulated in significant amounts. The data demonstrate that the analysis of glycoasparagines in amniotic fluid is not likely to permit reliable prenatal diagnosis of aspartylglycosaminuria.

Plasma vitamin C levels are low in premature infants fed human milk

To evaluate the vitamin C nutritional status of premature infants, plasma vitamin C concentrations were measured in 7 neonates born before 32 wk of gestation and in 13 premature infants born at or after 32 wk of gestation. Samples of umbilical venous plasma from 14 full-term infants were analyzed to provide reference values. Oral feedings with pooled, pasteurized milk from human donors were initiated 1-3 days after birth and intake was gradually increased to 200 ml X kg X day during the second week. After 2 wk, the 13 larger infants received approximately half of their daily milk intake from their own mothers. Results showed that plasma concentrations of vitamin C decline rapidly after birth and approach very low levels in preterm infants fed pasteurized, pooled human milk.

Liquid-chromatographic detection of aspartylglycosaminuria

We describe a specific, simple liquid-chromatographic method for detecting the lysosomal storage disease aspartylglycosaminuria. The method is based on identification and quantification of the major storage compound 2-acetamido-1-L-beta-aspartamido-1, 2-dideoxy-beta-D-glucose in the urine of affected individuals. Sample preparation and chromatographic analysis requires 30 min. Within-day variation of the method was less than 4.4%, between-day variation less than 11.7% (n = 10 each).

Liquid-chromatographic detection of aspartylglycosaminuria

We describe a specific, simple liquid-chromatographic method for detecting the lysosomal storage disease aspartylglycosaminuria. The method is based on identification and quantification of the major storage compound 2-acetamido-1-L-beta-aspartamido-1, 2-dideoxy-beta-D-glucose in the urine of affected individuals. Sample preparation and chromatographic analysis requires 30 min. Within-day variation of the method was less than 4.4%, between-day variation less than 11.7% (n = 10 each).

Isolation and partial characterization of keratan sulphate from human brain

A sulphated glycoconjugate was isolated from adult human brain from a glycosaminoglycan fraction which was not precipitated with 1% cetylpyridinium chloride or ethanol below 50% concentration. It appeared heterogeneous on gel filtration, exhibiting a molecular weight range from about 7000 to over 10 000. Its main covalent structure was shown to contain sulphated, repeating disaccharide units of (beta-D-galactose-(1----4)-N-acetyl-D-glucosamine-(1----3)). In addition, it was susceptible to degradation by keratan sulphate endo-beta-galactosidase and thus was assumed to be keratan sulphate.