A lethal phenotype associated with tissue plasminogen deficiency in humans

The role of plasminogen in preventing thrombosis requires activation by tissue plasminogen activator (t-PA) encoded by PLAT. While case-control associations have been pursued for common variants in PLAT, no disease-causing mutations have been reported. We describe a consanguineous family with two children who died shortly after birth due to complications related to severe hydranencephaly and diaphragmatic hernia. A combined exome/autozygome analysis was carried out with informed consent. We identified a homozygous null mutation in PLAT that abrogated t-PA level in patient cells. This is the first reported human knockout mutation of PLAT. The apparent association with hydranencephaly, diaphragmatic hernia and postnatal lethality requires further validation.

Identification of a novel MKS locus defined by TMEM107 mutation

Meckel-Gruber syndrome (MKS) is a perinatally lethal disorder characterized by the triad of occipital encephalocele, polydactyly and polycystic kidneys. Typical of other disorders related to defective primary cilium (ciliopathies), MKS is genetically heterogeneous with mutations in a dozen genes to date known to cause the disease. In an ongoing effort to characterize MKS clinically and genetically, we implemented a gene panel and next-generation sequencing approach to identify the causal mutation in 25 MKS families. Of the three families that did not harbor an identifiable causal mutation by this approach, two mapped to a novel disease locus in which whole-exome sequencing revealed the likely causal mutation as a homozygous splicing variant in TMEM107, which we confirm leads to aberrant splicing and nonsense-mediated decay. TMEM107 had been independently identified in two mouse models as a cilia-related protein and mutant mice display typical ciliopathy phenotypes. Our analysis of patient fibroblasts shows marked ciliogenesis defect with an accompanying perturbation of sonic hedgehog signaling, highly concordant with the cellular phenotype in Tmem107 mutants. This study shows that known MKS loci account for the overwhelming majority of MKS cases but additional loci exist including MKS13 caused by TMEM107 mutation.

Identification of embryonic lethal genes in humans by autozygosity mapping and exome sequencing in consanguineous families

Background

Identifying genetic variants that lead to discernible phenotypes is the core of Mendelian genetics. An approach that considers embryonic lethality as a bona fide Mendelian phenotype has the potential to reveal novel genetic causes, which will further our understanding of early human development at a molecular level. Consanguineous families in which embryonic lethality segregates as a recessive Mendelian phenotype offer a unique opportunity for high throughput novel gene discovery as has been established for other recessive postnatal phenotypes.

Results

We have studied 24 eligible families using autozygosity mapping and whole-exome sequencing. In addition to revealing mutations in genes previously linked to embryonic lethality in severe cases, our approach revealed seven novel candidate genes (THSD1, PIGC, UBN1, MYOM1, DNAH14, GALNT14, and FZD6). A founder mutation in one of these genes, THSD1, which has been linked to vascular permeability, accounted for embryonic lethality in three of the study families. Unlike the other six candidate genes, we were able to identify a second mutation in THSD1 in a family with a less severe phenotype consisting of hydrops fetalis and persistent postnatal edema, which provides further support for the proposed link between this gene and embryonic lethality.

Conclusions

Our study represents an important step towards the systematic analysis of “embryonic lethal genes” in humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0681-6) contains supplementary material, which is available to authorized users.

Accelerating novel candidate gene discovery in neurogenetic disorders via whole-exome sequencing of prescreened multiplex consanguineous families

Our knowledge of disease genes in neurological disorders is incomplete. With the aim of closing this gap, we performed whole-exome sequencing on 143 multiplex consanguineous families in whom known disease genes had been excluded by autozygosity mapping and candidate gene analysis. This prescreening step led to the identification of 69 recessive genes not previously associated with disease, of which 33 are here described (SPDL1, TUBA3E, INO80, NID1, TSEN15, DMBX1, CLHC1, C12orf4, WDR93, ST7, MATN4, SEC24D, PCDHB4, PTPN23, TAF6, TBCK, FAM177A1, KIAA1109, MTSS1L, XIRP1, KCTD3, CHAF1B, ARV1, ISCA2, PTRH2, GEMIN4, MYOCD, PDPR, DPH1, NUP107, TMEM92, EPB41L4A, and FAM120AOS). We also encountered instances in which the phenotype departed significantly from the established clinical presentation of a known disease gene. Overall, a likely causal mutation was identified in >73% of our cases. This study contributes to the global effort toward a full compendium of disease genes affecting brain function.

Fetal sex and leptin concentrations in pregnant females

BACKGROUND

Adult females have significantly more leptin than males. We investigated the effect of fetal sex on levels of leptin and other pregnancy hormones (progesterone, estradiol, FSH, LH and beta hCG) in pregnant females during different stages of pregnancy.

PATIENTS AND METHODS

Serum leptin levels in pregnant females followed at King Khaled University Hospital, Riyadh, Saudi Arabia in the year 2001 were estimated at the first, second, and third trimester of pregnancy as well as after delivery. Progesterone, estradiol, FSH, LH and beta hCG levels were also measured.

RESULTS

Leptin levels were significantly higher during all three trimesters in the pregnant females carrying female fetuses compared with those with male fetuses, while other hormones did not differ between the two groups. After delivery, the leptin levels decreased in both groups, and were still higher in the females who delivered baby girls, but the results were not statistically significant.

CONCLUSION

These finding suggests that leptin might play a role in sex regulation during embryonic development.

Correlates of age at menopause and osteoporosis in Saudi women

OBJECTIVE

To evaluate the age of menopause among Saudi Arabian women and to predict the local trend in the prevalence of osteoporosis.

MATERIAL & METHOD

All menopausal women who had bone mineral density studies at King Khaled University Hospital, Riyadh, Saudi Arabia, between 1999 to 2003. Correspondence and logistic regression analysis were conducted to identify variables that were positively associated with age of menopause.

RESULTS

935 postmenopausal females were included. The mean age of menopause was 48.1 +/- 5.9 years. Early and late onset of menopause were associated with osteoporosis, while normal onset of menopause was associated with osteopenia or remained normal. There was no association between age of menopause and parity or body mass index.

CONCLUSION

The age of menopause among Saudi women is lower than in Western countries but similar to other Arabic countries. In addition to cultural differences genetics play a role in determining the age of menopause and the development of osteoporosis.

Serum cystatin C in pregnant women: reference values, reliable and superior diagnostic accuracy

BACKGROUND

A simple, endogenous, accurate and minimally invasive marker of glomerular filtration rate (GFR) is much desired in clinical nephrology. Cystatin C fulfills all criteria to be a marker for GFR. For early detection of renal impairment in pregnant women, it is necessary to determine serum cystatin C reference values and the correlation with GFR. The present study was therefore undertaken.

METHOD

Healthy pregnant women were followed during pregnancy and the postnatal period. Patient demographics included age, height, weight, BMI, parity, total blood count, LFT, urea, creatinine, Na, K, and blood sugar. Serum cystatin C was estimated using particle enhanced nephlo-immunoassay method. All the parameters were recorded at the start of pregnancy and then in each trimester and the postnatal period. Regression analysis correlation coefficient, ANOVA and the Student's t-test were used for analysis using the SPSS statistical package.

RESULTS

A total of 197 pregnant women were included. Mean serum cystatin C for all the women was 0.82 +/- 0.184 mg/l. Serum cystatin C levels were high -0.89 +/- 0.12 mg/l in the first trimester, decreased significantly to 0.651 +/- 0.14 mg/l during the second trimester (p = 0.0000 compared to first trimester), and increased again to 0.82 +/- 0.191 mg/l in the third trimester. After delivery the level rose to 0.94 +/- 0.12 mg/l. A strong correlation was found between serum cystatin C and serum creatinine. A strong negative correlation was found between GFR and cystatin C values in the women (r = -0.546, p = 0.000). A linear relationship was found between GFR and cystatin C levels. A significant increase in the GFR was noted with the progression of pregnancy from 128.06 +/- 29.7 ml/min in the first trimester to 155.2 +/- 29.59 ml/min during second trimester (p = 0.006). A decline in the level of cystatin C exactly parallel to the increase in the GFR was noted with the progression of pregnancy. Interestingly cystatin C was found to have a strong negative correlation with gestational age (r = -0.663, p = 0.000).

CONCLUSION

Our results indicate that the mean serum cystatin C levels reflect changes in the GFR during the entire pregnancy and also in the postnatal period. Moreover, serum cystatin C levels are independent of age, height, weight, or blood sugar level. Cystatin C can be used for close supervision and early diagnosis of renal impairment in pregnant patients. Cystatin C is a reliable, useful and promising marker of GFR in pregnant women.

Leptin concentration during different stages of pregnancy

OBJECTIVES

To determine the levels of leptin in pregnant females during different stages of pregnancy and to correlate these levels to maternal weight, body mass index (BMI), neonate weight and neonate BMI.

MATERIAL & METHODS

A case control study was carried out in which 60 pregnant females were enrolled, but only 36 completed the study and 30 non-pregnant females were used as controls. Blood samples were collected at the 1st trimester, 2nd trimester and 3rd trimester, and after delivery. Serum was used for the estimation of leptin (by radioimmunoassay).

RESULTS

The results showed that the levels of leptin were significantly higher in pregnant females compared to non-pregnant females, but significantly decreased after delivery. In pregnant females with gestational diabetes the leptin level was insignificantly higher.

CONCLUSION

The increase of leptin levels may be due to the stimulatory effect of insulin on leptin secretion from adipose tissue.