Identification of XLRS1 Gene Mutation (608C>T) in a Portuguese Family with Juvenile Retinoschisis

Purpose

To characterize electroretinogram (ERG) and molecular genetic findings in a family with XLRS1 mutation. The authors present two cases of a Portuguese family with juvenile retinoschisis with a mutation in exon 6.

Methods

Two brothers and their parents, grandmother, and uncle underwent a full ophthalmic examination. The two brothers with ophthalmic disease were evaluated with color fundus photography, fluorescein angiography, optical coherence tomography (OCT), molecular genetic study (Group VI of Retinoschisis Consortium), pattern visual evoked potential (PVEP), and full field ERG.

Results

Both patients presented funduscopic manifestations of vitreoretinal degeneration. They presented peripheral schisis and retinal detachment. However, foveal schisis had never been observed at funduscopy. A negative ERG was recorded in both. Six months after that, the younger brother showed a typical foveal schisis at fundus examination. A retinoschisis gene (XLRS1) mutation with transition of cytosine by thymine at position 608 (608C>T) had been identified in both.

Conclusions

Negative ERG is the most secure clinical marker to establish the diagnosis of juvenile retinoschisis. XLRS1 gene 608C>T mutation was described for the first time in a Portuguese family.

Tyrosinemia type II: Mutation update, 11 novel mutations and description of 5 independent subjects with a novel founder mutation

BACKGROUND

Tyrosinemia type II, also known as Richner-Hanhart Syndrome, is an extremely rare autosomal recessive disorder, caused by mutations in the gene encoding hepatic cytosolic tyrosine aminotransferase, leading to the accumulation of tyrosine and its metabolites which cause ocular and skin lesions, that may be accompanied by neurological manifestations, mostly intellectual disability.

AIMS

To update disease-causing mutations and current clinical knowledge of the disease.

MATERIALS AND METHODS

Genetic and clinical information were obtained from a collection of both unreported and previously reported cases.

RESULTS

We report 106 families, represented by 143 individuals, carrying a total of 36 genetic variants, 11 of them not previously known to be associated with the disease. Variants include 3 large deletions, 21 non-synonymous and 5 nonsense amino-acid changes, 5 frameshifts and 2 splice variants. We also report 5 patients from Gran Canaria, representing the largest known group of unrelated families sharing the same P406L mutation.

CONCLUSIONS

Data analysis did not reveal a genotype-phenotype correlation, but stressed the need of early diagnosis: All patients improved the oculocutaneous lesions after dietary treatment but neurological symptoms prevailed. The discovery of founder mutations in isolated populations, and the benefits of early intervention, should increase diagnostic awareness in newborns.

X-linked retinoschisis maculopathy treated with topical dorzolamide, and relationship to genotype

PURPOSE

To correlate the response of topical dorzolamide (Trusopt; Merck) in patients with X-linked retinoschisis (XLRS) with genotype.

METHODS

We carried out a retrospective evaluation of four patients (seven eyes) with XLRS, treated with topical dorzolamide. The change in best-corrected visual acuity (VA) and central macular thickness (CMT; central 1 mm subfield thickness) from optical coherence tomography (OCT) was analysed over the follow-up period, using Student's t-test. Each patient also had genetic analysis for mutations in the retinoschisisgene (RS1).

RESULTS

The mean age at the start of treatment was 14.7±11 years, and mean follow-up duration was 21.7±7.7 months. Mean CMT at the final follow-up was significantly better than at baseline (291±123 vs 352±119 μm, P=0.007); however, mean VA was worse (0.38±0.25 vs 0.31±0.24 logMAR score, P=0.041). All four patients had a mutation in the RS1gene; there was no apparent association between the type of mutation and the response to topical dorzolamide.

CONCLUSION

Topical dorzolamide may have some effect in reducing central macular thickness in patients with XLRS, but this does not necessarily correlate with improvement in VA. In our case series, genotypic information did not predict the response to this treatment.

Rates of loss of heterozygosity and mitotic recombination in NF2 schwannomas, sporadic vestibular schwannomas and schwannomatosis schwannomas

Biallelic inactivation of the NF2 gene occurs in the majority of schwannomas. This usually involves a combination of a point mutation or multiexon deletion, in conjunction with either a second point mutation or loss of heterozygosity (LOH). We have performed DNA sequence and dosage analysis of the NF2 gene in a panel of 239 schwannoma tumours: 97 neurofibromatosis type 2 (NF2)-related schwannomas, 104 sporadic vestibular schwannomas (VS) and 38 schwannomatosis-related schwannomas. In total, we identified germline NF2 mutations in 86 out of 97 (89%) NF2 patients and a second mutational event in 77 out of 97 (79%). LOH was by far the most common form of second hit. A combination of microsatellite analysis with either conventional comparative genomic hybridization (CGH) or multiplex ligation-dependent probe amplification (MLPA) identified mitotic recombination (MR) as the cause of LOH in 14 out of 72 (19%) total evaluable tumours. Among sporadic VS, at least one NF2 mutation was identified by sequence analysis or MLPA in 65 out of 98 (66%) tumours. LOH occurred in 54 out of 96 (56%) evaluable tumours, but MR only accounted for 5 out of 77 (6%) tested. LOH was present in 28 out of 34 (82%) schwannomatosis-related schwannomas. In all eight patients who had previously tested positive for a germline SMARCB1 mutation, this involved loss of the whole, or part of the long arm, of chromosome 22. In contrast, 5 out of 22 (23%) tumours from patients with no germline SMARCB1 mutation exhibited MR. High-resolution Affymetrix SNP6 genotyping and copy number (CN) analysis (Affymetrix, Santa Clara, CA, USA) were used to determine the chromosomal breakpoint locations in tumours with MR. A range of unique recombination sites, spanning approximately 11.4 Mb, were identified. This study shows that MR is a mechanism of LOH in NF2 and SMARCB1-negative schwannomatosis-related schwannomas, occurring less frequently in sporadic VS. We found no evidence of MR in SMARCB1-positive schwannomatosis, suggesting that susceptibility to MR varies according to the disease context.

SMARCB1 mutations are not a common cause of multiple meningiomas

BACKGROUND

Schwannomas and meningiomas are both part of the tumour spectrum of neurofibromatosis type 2 (NF2) and are associated with somatic loss of chromosome 22. They are also found commonly within the general population, unrelated to NF2. Germline SMARCB1 mutations have recently been identified as a pathogenic cause of a subset of familial schwannomatosis cases, and SMARCB1 is a candidate gene for causation of both schwannomas and meningiomas. Recently, Bacci et al reported a germline SMARCB1 mutation associated with familial schwannomatosis and multiple meningiomas. They concluded that SMARCB1 mutations can predispose to multiple meningiomas.

METHODS

We screened the SMARCB1 gene in a panel of 47 patients with multiple meningioma unrelated to NF2.

RESULTS

We found no germline mutations.

CONCLUSION

We conclude that while meningiomas may be associated with the schwannomatosis phenotype, SMARCB1 is not a major contributor to multiple meningioma disease.

Correlations between clinical and physiological consequences of the novel mutation R878C in a highly conserved pore residue in the cardiac Na+ channel

Aim:

We compared the clinical and physiological consequences of the novel mutation R878C in a highly conserved pore residue in domain II (S5-S6) of human, hNa_v1.5, cardiac Na⁺ channels.

Methods:

Full clinical evaluation of pedigree members through three generations of a Chinese family combined with SCN5A sequencing from genomic DNA was compared with patch and voltage-clamp results from two independent expression systems.

Results:

The four mutation carriers showed bradycardia, and slowed sino-atrial, atrioventricular and intraventricular conduction. Two also showed sick sinus syndrome; two had ST elevation in leads V1 and V2. Unlike WT-hNa_v1.5, whole-cell patch-clamped HEK293 cells expressing R878C-hNa_v1.5 showed no detectable Na⁺ currents (i_Na), even with substitution of a similarly charged lysine residue. Voltage-clamped Xenopus oocytes injected with either 0.04 or 1.5 μg μL⁻¹ R878C-hNa_v1.5 cRNA similarly showed no i_Na, yet WT-hNa_v1.5 cRNA diluted to 0.0004–0.0008 ng μL⁻¹resulted in expression of detectable i_Na. i_Na was simply determined by the amount of injected WT-hNa_v1.5: doubling the dose of WT-hNa_v1.5 cRNA doubled i_Na. i_Na amplitudes and activation and inactivation characteristics were similar irrespective of whether WT-hNa_v1.5 cRNA was given alone or combined with equal doses of R878C-hNa_v1.5 cRNA therefore excluding dominant negative phenotypic effects. Na⁺ channel function in HEK293 cells transfected with R878C-hNa_v1.5 was not restored by exposure to mexiletine (200 μm) and lidocaine (100 μm). Fluorescence confocal microscopy using E3-Nav1.5 antibody demonstrated persistent membrane expression of both WT and R878C-hNa_v1.5. Modelling studies confirmed that such i_Na reductions reproduced the SSS phenotype.

Conclusion:

Clinical consequences of the novel R878C mutation correlate with results of physiological studies.

Molecular characterisation of SMARCB1 and NF2 in familial and sporadic schwannomatosis

BACKGROUND

Schwannomatosis is a rare condition characterised by multiple schwannomas and lack of involvement of the vestibular nerve. A recent report identified bi-allelic mutations in the SMARCB1/INI1 gene in a single family with schwannomatosis. We aimed to establish the contribution of the SMARCB1 and the NF2 genes to sporadic and familial schwannomatosis in our cohort.

METHODS

We performed DNA sequence and dosage analysis of SMARCB1 and NF2 in 28 sporadic cases and 15 families with schwannomatosis.

RESULTS

We identified germline mutations in SMARCB1 in 5 of 15 (33.3%) families with schwannomatosis and 2 of 28 (7.1%) individuals with sporadic schwannomatosis. In all individuals with a germline mutation in SMARCB1 in whom tumour tissue was available, we detected a second hit with loss of SMARCB1. In addition, in all affected individuals with SMARCB1 mutations and available tumour tissue, we detected bi-allelic somatic inactivation of the NF2 gene. SMARCB1 mutations were associated with a higher number of spinal tumours in patients with a positive family history (p = 0.004).

CONCLUSION

In contrast to the recent report where no NF2 mutations were identified in a schwannomatosis family with SMARCB1 mutations, in our cohort, a four hit model with mutations in both SMARCB1 and NF2 define a subset of patients with schwannomatosis.

Randomized trial of toremifene to reduce high grade prostatic intraepithelial neoplasia (HGPIN) prior to radical prostatectomy (RP)

5150

Background HGPIN may be a precursor lesion for prostate cancer (PCA). The selective estrogen-receptor modulator toremifene (TOR) has shown chemopreventive activity in preclinical models of PCA. The effect of TOR on HGPIN was studied in men with PCA prior to RP. Methods Men with biopsy-proven PCA, scheduled for RP were randomized (2:1) either to TOR 40 mg po qd for 3 to 6 weeks prior to RP or to no therapy. The primary endpoint was the proportion of HGPIN in the RP specimen. Planned sample sizes were 35 and 17 per arm respectively, providing 93% power if treatment increased the proportion of patients with no RP HGPIN from 15% to 35% and decreased the mean log nonzero HGPIN values from 1 to ¼ standard deviation. Expression of bcl2, ki67, and CD31 were determined on biopsy (BX), and RP tissues, separately for normal adjacent to tumor (NAT), HGPIN, and PCA tissues. Serum hormone levels and toxicity were also assessed. Results The treatment arm accrued 31 patients, the control arm 13 patients. RP HGPIN ranged from 0.5% to 12%. There was no difference in HGPIN means between treatment (3.8%) and control (3.3%) (P=0.77 one-sided Wilcoxon) HGPIN at baseline predicted HGPIN at RP (Spearman correlation=0.64, P=0.0005) but 66% of patients had no detected HGPIN at baseline. Bcl2, ki67, and CD31 were mutually positively correlated in all 3 tissues, in both BX and RP specimens. In both BX and RP specimens, bcl2 was highest by far in HGPIN, and lowest in PCA. Ki67 was lowest in NAT, elevated in HGPIN and highest in PCA. CD31 showed no differences. In treated patients but not in controls, dihydrotestosterone, testosterone, androstenedion, and estradiol increased significantly between baseline, day 14 and final. TOR was well tolerated. Conclusions These data do not support an effect of TOR on HGPIN over 3 to 6 weeks at 40 mg po qd.

No significant financial relationships to disclose.

Can 1H-Nuclear magnetic resonance (NMR) be used for early detection of hepatocellular cancer (HCC)?

15107

Background: HCC is a common and rapidly fatal cancer. Current screening tools are inadequate for identification of potentially curable cases. Our aim was to determine whether H-NMR can identify HCC compared to controls in the woodchuck (WC) model of hepatitis related HCC. Methods: Eastern WCs were bred and inoculated at birth with dilute sera from WCs that are chronic carriers of Woodchuck Hepatitis B Virus (WHV). This resulted in chronic hepatitis in ∼60% animals and all carriers developed HCC by 24–36 months. Serum from 10 chronic WHV carriers with HCC (group 1), 5 WHV carriers with no HCC (group 2) and 15 matched non-infected controls (group 3) was obtained. 45uL serum was diluted with 5uL of D2O containing 27mM formic acid + 0.9% saline. Spectra were collected on a 600 MHz INOVA spectrometer using a CapNMR flow probe with 10uL flow cell at 298K without knowledge of group assignments. The resulting 1D spectra were processed using Nuts from AcornNMR. Results: Principle component analysis and supervised PLS-DA was performed using Simca P+ from Umetrics. Despite general separation of groups, the Q2 value of this model was relatively low (0.20). We trained a Support Vector Machine (SVM) algorithm, a supervised machine-learning algorithm, to learn to identify the groups. Evaluation of the performance of the algorithm using 10-fold validation on the data set achieved a Kappa value of 0.43. This algorithm learnt to identify HCC [0.765 ROC, 0.8 sensitivity, and 0.727 positive predictive value (PPV)] and controls (0.75 ROC, 0.69 sensitivity and 0.73 PPV) but not the WHV carrier group, likely due to the small numbers. In a second analysis of 10 HCC and 15 controls, PLS-DA showed clear separation using three components (Q2= 0.5). The corresponding SVM model showed a kappa value of 0.52 and ROC values of 0.767 for both classes. Conclusions: Our preliminary results indicate that H-NMR spectra alone can be used to distinguish HCC from healthy controls using the machine-learning algorithm for classification. Further validation in a larger cohort of woodchucks is ongoing and confirmation of these preliminary findings would support investigation of this technique as a screening tool in patients at risk for developing HCC.

No significant financial relationships to disclose.

Inherited association of breast and colorectal cancer: limited role of CHEK2 compared with high-penetrance genes

We assessed the association between breast cancer (BC) and colorectal cancer (CRC) from referral pattern to the Regional Genetics Service including molecular analysis. Hospital computer records and/or department referral books were used to identify cases referred to the Regional Genetic Service during a 16-year period (1990-2005 inclusive). All files were reviewed along with associated demographic data, risk assessments, referral details and results from mutation testing. Families were assessed for hereditary breast and colorectal cancer (HBCC) criteria, and all families with eligible individuals were tested for the 1100delC mutation in CHEK2. A total of 8,612 families were identified. One hundred and sixteen of 1,631 (7.5%) families with a primary referral for CRC fulfilled the criteria for HBCC, whereas only 68/6981 (1%) BC referrals fulfilled these criteria. Blood samples were obtained from 113 individuals from 83/184 families. Only 1/113 (1%) has screened positive for the CHEK2 mutation, whereas 14 (17%) families segregate BRCA1/2 mutations and at least 7 (8.5%) carry MLH1/MSH2 mutations. HBCC syndrome, if it exists as a separate entity, is not likely to be due to CHEK2 mutations. Many families are explicable by existing high-penetrance genes, and further work is necessary to elucidate whether the remainder is due to chance or as yet undiscovered genes.

A phase I study of vorinostat (suberoylanilide hydroxamic acid, SAHA) in combination with 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) in patients with advanced colorectal cancer (CRC)

3592

Background: Vorinostat is a novel histone deacetylase (HDAC) inhibitor that potentiates 5-FU and platinum antitumor activity. This potentiation is associated with ∼ 40 fold decrease in thymidilate synthase (TS) expression, the main target of 5-FU, in preclinical models. We conducted a phase I study of vorinostat plus FOLFOX in patients with CRC to determine the recommended dose of this combination. Methods: Vorinostat was escalated in a standard 3+3 design. FOLFOX was administered at a fixed dose every 2 weeks: leucovorin 400mg/m2 and oxaliplatin 85mg/m2 over 2 hours followed by 5-FU bolus 400mg/m2 and 5-FU infusion 2400mg/m2 over 46 hours. Vorinostat started 3 days prior to FOLFOX and was given twice daily for 1 week followed by 1 week break. Investigated dose levels of vorinostat (twice daily) include 100, 200, and 300 mg. Tumor biopsies were obtained from patients with accessible liver metastases before and on the 4th day of vorinostat (prior to FOLFOX) to assess TS expression. Results: 9 patients (pts) enrolled (M/F: 8/1; median age: 57, ECOG 0/1: 5/4). All pts had failed prior FOLFOX, irinotecan, and cetuximab therapy. One pt at dose level (DL) 1 was not evaluable due to rapid clinical progression. No dose-limiting toxicities were noted among the 8 evaluable pts. No grade (G) 3 toxicities were noted on the first cycle of treatment (within 2 weeks after 1st FOLFOX) and accrual continues on DL3. Cycle 1 toxicities were attributed to FOLFOX and consisted of 1 G2 neutropenia, 1 G2 mucositis, and 2 G2 nausea/vomiting. Responses were evaluable in 6 pts: 1 pt with peritoneal carcinomatosis on DL 1 has stable disease 5 months + along with a stable CEA; 3 patients at DL2 have stable disease at 2 months along with declining CEA in 2/3 pts. Two pts (DL1) with liver metastases biopsies had a major decrease in TS expression by IHC after 4 days of vorinostat. Conclusions: Vorinostat at 100–200mg PO BID × 1 week every 2 weeks in combination with FOLFOX is well tolerated. The lowest DL of 100 mg PO BID is associated with down-regulation of TS. Disease stabilization in highly refractory patients is promising. The investigation of this regimen in the first or second-line treatment of metastatic CRC is warranted.

No significant financial relationships to disclose.

Phase I, pharmacokinetic (PK), pharmacodynamic study of paricalcitol [19-nor-1 alpha, 25-(OH)2 D2] in combination with gemcitabine [2’,2’ difluorodeoxycytidine] in patients with advanced malignancies

12010

Background: Calcitriol+ gemcitabine (gem) combination results in synergistic anti-tumor effect in preclinical models. Cytidine deaminase (CDD) inactivates gem into 2’,2’-difluorodeoxyuridine (dFdU) and its overexpression may lead to gem resistance. Calcitriol decreases CDD activity in peripheral blood mononuclear cells (PBM). Paricalcitol is cytotoxic in vitro and synergistic with several chemotherapeutic agents, including gem. We are conducting a phase I study of paricalcitol + fixed-dose gem. Objectives: The primary aim is to determine maximum tolerated dose (MTD) of the combination in patients (pts) with advanced cancer. Secondary aims are to evaluate toxicity, the effect of paricalcitol on gem PK, CDD activity in PBM and clinical outcome. Methods: Each cycle is 4 weeks: Gem 800 mg/m2 (over 80 min) weekly × 3, starting day 1; paricalcitol weekly, 24 h prior to gem, starting day 7. Standard 3+3 dose-escalation schema is used. Planned paricalcitol doses are 0.24, 0.72, 1.20, 1.8, 2.4 μg/kg, and 25% increments till MTD. Gem PK and CDD activity (PBM) are studied on days 1 and 8. Paricalcitol PK studies are obtained on day 7. Results: Fourteen pts with the following cancers: pancreatic (n=3), colon (n=3), lung (n=5), esophageal (n=1), bladder (n=1) and unknown primary (n=1) have been enrolled. No dose limiting toxicities have occurred. Median of 2 cycles were delivered (range 1–9). Grade 3 toxicities: anemia (n=3 pts), neutropenia (n=5), thrombocytopenia (n=3), thrombosis (n=2), anorexia (n=1), hypophosphatemia (n=1), dehydration (n=1), syncope (n=1), pneumonia (n=1) and chills (n=1). Grade 4 toxicities: anemia (n=1) and neutropenia (n=1). Hypercalcemia (> grade 1) did not occur. Stable disease occurred in 2 and progressive disease in 3. Conclusions: MTD was not reached at 1.8 μg/kg of paricalcitol with gem 800 mg/m2/week. Dose escalation is ongoing. PK data will be presented at meeting. Supported by NIH grants CA67267 and CA85142.

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X-linked retinoschisis: clinical phenotype and RS1 genotype in 86 UK patients

BACKGROUND

Inactivating mutations of the gene RS1 lead to X-linked retinoschisis, a progressive retinal dystrophy characterised by schisis within the inner layers of the neuroretina. The mutation spectrum is large and the phenotype variable.

AIM

To determine whether there is a correlation between mutation type and disease severity.

METHODS

We identified the causative mutation in 86 affected patients and examined each of these patients in detail. Different categories of mutation were compared for each phenotypic characteristic.

RESULTS

We found a reduction in visual acuity with increasing age and worsening macular pathology in patients over 30 years old (p < or = 0.001), but there was no correlation between mutation type and severity of disease. Furthermore, we found a wide variation in phenotype even within families.

CONCLUSIONS

Identifying the causative mutation in patients with X-linked retinoschisis is helpful in confirming diagnosis and in counselling of family members but cannot be used to predict prognosis for an individual patient.

Is Optic Nerve Fibre Mis-Routing a Feature of Congenital Stationary Night Blindness?

PURPOSE

To determine whether patients with congenital stationary night blindness (CSNB) have electrophysiological evidence of optic nerve fibre mis-routing similar to that found in patients with ocular albinism (OA).

METHOD

We recorded the Pattern Onset VEP using a protocol optimised to detect mis-routing of optic nerve fibres in older children and adults. We tested 20 patients (age 15-69 yrs) with X-linked or autosomal recessive CSNB, 14 patients (age 9-56 yrs) with OA and 13 normally pigmented volunteers (age 21-66 yrs). We measured the amplitude and latency of the CI component at the occipital midline and over left and right occipital hemispheres. We also assessed the computed inter-hemispheric "difference" signal. Subjects with CSNB were classified as having the "complete" or "incomplete" phenotype on the basis of their ERG characteristics. Members of X-linked CSNB pedigrees underwent mutation screening of the NYX and CACNA1F genes.

RESULTS

CI was significantly smaller over the ipsilateral hemisphere and more prominent over the contralateral hemisphere in OA patients compared with both controls and CSNB patients. In CSNB patients CI response amplitudes were not significantly different from controls but peak latency was prolonged at all three electrodes compared with controls. The inter-hemispheric "difference" signal was abnormal for the OA group but not for the CSNB group. Contralateral dominance of CI could be identified in the majority of OA patients and the "difference" signal was opposite in polarity for left compared with right eye stimulation in every patient in this group. Only 3 of 20 patients with CSNB showed significant inter-hemispheric asymmetry similar to that seen in the OA patients. All 3 CSNB patients with evidence for optic nerve fibre mis-routing had X-linked pedigrees: 2 had an identified mutation in the NYX gene but no mutation in either the NYX or CACNA1F genes was identified in the third. VEP evidence of optic nerve fibre mis-routing was present in 3 of the 11 subjects with "complete" phenotype and none of the 9 patients with "incomplete" phenotype CSNB.

CONCLUSION

Mis-routing of optic nerve fibres does occur in CSNB but we found evidence of it in only 15% of our patients.

Molecular pathology of X linked retinoschisis: mutations interfere with retinoschisin secretion and oligomerisation

BACKGROUND/AIM

X linked retinoschisis (XLRS) is caused by mutations in RS1 which encodes the discoidin domain protein retinoschisin, secreted by photoreceptors and bipolar cells. Missense mutations occur throughout the gene and some of these are known to interfere with protein secretion. This study was designed to investigate the functional consequences of missense mutations at different locations in retinoschisin.

METHODS AND RESULTS

The authors developed a structural model of the retinoschisin discoidin domain and used this to predict the effects of missense mutations. They expressed disease associated mutations and found that those affecting conserved residues prevented retinoschisin secretion. Most of the remaining mutations cluster within a series of loops on the surface of the beta barrel structure and do not interfere with secretion, suggesting this region may be a ligand binding site. They also demonstrated that wild type retinoschisin octamerises and associates with the cell surface. A subgroup of secreted mutations reduce oligomerisation (C59S, C219G, C223R).

CONCLUSIONS

It is suggested that there are three different molecular mechanisms which lead to XLRS: mutations interfering with secretion, mutations interfering with oligomerisation, and mutations that allow secretion and oligomerisation but interfere with retinoschisin function. The authors conclude that binding of oligomerised retinoschisin at the cell surface is important in its presumed role in cell adhesion.

Identification of XLRS1 gene mutation (608C > T) in a Portuguese family with juvenile retinoschisis

PURPOSE

To characterize electroretinogram (ERG) and molecular genetic findings in a family with XLRS1 mutation. The authors present two cases of a Portuguese family with juvenile retinoschisis with a mutation in exon 6.

METHODS

Two brothers and their parents, grandmother, and uncle underwent a full ophthalmic examination. The two brothers with ophthalmic disease were evaluated with color fundus photography, fluorescein angiography, optical coherence tomography (OCT), molecular genetic study (Group VI of Retinoschisis Consortium), pattern visual evoked potential (PVEP), and full field ERG.

RESULTS

Both patients presented funduscopic manifestations of vitre o retinal degeneration. They presented peripheral schisis and retinal detachment. However, foveal schisis had never been observed at funduscopy. A negative ERG was recorded in both. Six months after that, the younger brother showed a typical foveal schisis at fundus examination. A retinoschisis gene (XLRS1) mutation with transition of cytosine by thymine at position 608 (608C > T) had been identified in both.

CONCLUSIONS

Negative ERG is the most secure clinical marker to establish the diagnosis of juvenile retinoschisis. XLRS1 gene 608C > T mutation was described for the first time in a Portuguese family.

Identification of XLRS1 gene mutation (608C>T) in a Portuguese family with juvenile retinoschisis

PURPOSE

To characterize electroretinogram (ERG) and molecular genetic findings in a family with XLRS1 mutation. The authors present two cases of a Portuguese family with juvenile retinoschisis with a mutation in exon 6.

METHODS

Two brothers and their parents, grandmother, and uncle underwent a full ophthalmic examination. The two brothers with ophthalmic disease were evaluated with color fundus photography, fluorescein angiography, optical coherence tomography (OCT), molecular genetic study (Group VI of Retinoschisis Consortium), pattern visual evoked potential (PVEP), and full field ERG.

RESULTS

Both patients presented funduscopic manifestations of vitre o retinal degeneration. They presented peripheral schisis and retinal detachment. However, foveal schisis had never been observed at funduscopy. A negative ERG was recorded in both. Six months after that, the younger brother showed a typical foveal schisis at fundus examination. A retinoschisis gene (XLRS1) mutation with transition of cytosine by thymine at position 608 (608C>T) had been identified in both.

CONCLUSIONS

Negative ERG is the most secure clinical marker to establish the diagnosis of juvenile retinoschisis. XLRS1 gene 608C>T mutation was described for the first time in a Portuguese family. (Eur J Ophthalmol 2005; 15: 638-40 ).

Learning and behavioural difficulties but not microcephaly in three brothers resulting from undiagnosed maternal phenylketonuria

Universal screening introduced in the 1960s has reduced the incidence of learning disability resulting from phenylketonuria (PKU), which is a treatable condition. Nonetheless, PKU may still be having an impact on the paediatric-age population. We report a woman with previously undiagnosed PKU who was born before the onset of universal screening. She is of normal intelligence, and so the diagnosis was not suspected until after the birth of her three children. Her serum phenylalanine concentration was found to be in excess of 1 mmol/L, well into the toxic range. She has had three sons, all of whom have a significant degree of learning disability resulting from intrauterine exposure to toxic levels of phenylalanine. None of the sons had microcephaly, a physical sign that, if present, might have helped to point towards the correct diagnosis. We suggest that maternal PKU should be suspected where there is sibling recurrence of cognitive impairment, particularly where the mother was born before the initiation of the neonatal screening programme for PKU.

Genotype-phenotype correlation in British families with X linked congenital stationary night blindness

AIM

To correlate the phenotype of X linked congenital stationary night blindness (CSNBX) with genotype.

METHODS

11 CSNB families were diagnosed with the X linked form of the disease by clinical evaluation and mutation detection in either the NYX or CACNA1F gene. Phenotype of the CSNBX patients was defined by clinical examination, psychophysical, and standardised electrophysiological testing.

RESULTS

Comprehensive mutation screening identified NYX gene mutations in eight families and CACNA1F gene mutations in three families. Electrophysiological and psychophysical evidence of a functioning but impaired rod system was present in subjects from each genotype group, although the responses tended to be more severely affected in subjects with NYX gene mutations. Scotopic oscillatory potentials were absent in all subjects with NYX gene mutations while subnormal OFF responses were specific to subjects with CACNA1F gene mutations.

CONCLUSIONS

NYX gene mutations were a more frequent cause of CSNBX than CACNA1F gene mutations in the 11 British families studied. As evidence of a functioning rod system was identified in the majority of subjects tested, the clinical phenotypes "complete" and "incomplete" do not correlate with genotype. Instead, electrophysiological indicators of inner retinal function, specifically the characteristics of scotopic oscillatory potentials, 30 Hz flicker and the OFF response, may prove more discriminatory.

Toxicity and response evaluation of the interferon inducer poly ICLC administered at low dose in advanced renal carcinoma and relapsed or refractory lymphoma: a report of two clinical trials of the Eastern Cooperative Oncology Group

PURPOSE

Phase II studies were conducted to evaluate the safety and efficacy of the interferon inducer Poly ICLC at low doses in advanced renal cancer and relapsed or refractory lymphoma.

PATIENTS AND METHODS

Twenty-nine patients with advanced renal carcinoma and eleven patients with lymphoma were treated with poly ICLC. Patients received 0.25 mg/m2 of poly ICLC intravenously twice weekly three days apart until progression or unacceptable toxicity.

RESULTS

There were no objective responses. Six patients with renal carcinoma had stable disease as best response with one patient receiving 62 weeks of therapy. Toxicity included grade 3 anemia in 8 patients and grade 4 anemia in one patient. All patients were anemic prior to entry with a median grade 2 anemia at baseline. Grade 4 neutropenia, thrombocytopenia and injection site pain occurred in one patient each. Grade 3 fever, chills or fatigue occurred in four, three, and three patients respectively. Any grade fever occurred in 10 patients (25.6%) and any grade chills occurred in 9 patients (23.1%).

CONCLUSION

Poly ICLC at this dose and schedule is well tolerated in both patient populations and is inactive in renal carcinoma.

Prevalence and incidence of hepatitis C virus infection in the US military: a seroepidemiologic survey of 21,000 troops

Because of a high prevalence of hepatitis C virus (HCV) infection (10-20%) among veterans seeking care in Department of Veterans Affairs (VA) hospitals, current US military forces were evaluated for HCV infection. Banked serum samples were randomly selected from military personnel serving in 1997 and were tested for antibody to HCV (anti-HCV). Overall prevalence of anti-HCV among 10,000 active-duty personnel was 0.48% (5/1,000 troops); prevalence increased with age from 0.1% among military recruits and active-duty personnel aged <30 years to 3.0% among troops aged >/=40 years. Prevalence among 2,000 Reservists and active-duty troops was similar. Based on sequential serum samples from 7,368 active-duty personnel (34,020 person-years of observation), annual incidence of infection was 2/10,000. Of 81 HCV RNA-positive troops for whom genotype was determined, genotypes 1a (63%) and 1b (22%) predominated, as in the civilian population. These data indicate that HCV infection risk among current military forces is lower than in VA studies and the general civilian population aged <40 years. The low level of HCV infection may be attributed to infrequent injection drug use in the military due to mandatory testing for illicit drugs prior to induction and throughout military service.

Mutations of the XLRS1 gene cause abnormalities of photoreceptor as well as inner retinal responses of the ERG

Intensity-series rod and cone ERGs were recorded in 19 patients with XLRS and 26 control eyes. All patients were examined by one ophthalmologist and diagnosed on the basis of fundus appearance and evidence of the disease in other males in the same family. Mutations in the XLRS1 gene have been identified in 15 of the patients. Dark-adapted ERGs were significantly different from controls for all test conditions and for both a-wave and b-wave responses. Abnormalities were detectable in all patients but there was considerable variation in the severity of abnormality. One third of the patients had the dark-adapted 'negative-wave' response typically associated with inner retinal disorder, but about one third showed only mild depression of the b-wave while the remainder had abnormally low a-waves in addition to depressed b-waves. Light-adapted responses were also affected and both a-wave and b-wave responses differed significantly from controls, but the 'negative-wave' response was not seen in any patient. The severity of the ERG abnormality did not correlate with the classification of fundus appearance or patient age suggesting that retinal function is relatively stable throughout life. The severity of ERG abnormalities did not correlate with the type of mutation and responses could differ between affected males within the same family. These results indicate considerable heterogeneity of ERG response without clinical, age or genetic correlate. The abnormal a-wave responses indicate that photoreceptor as well as inner retinal layer function may be affected in XLRS, at least in some patients.

Retinoschisin, the X-linked retinoschisis protein, is a secreted photoreceptor protein, and is expressed and released by Weri-Rb1 cells

X-linked retinoschisis is characterized by microcystic-like changes of the macular region and schisis within the inner retinal layers, leading to visual deterioration in males. Many missense and protein-truncating mutations of the causative gene RS1 have now been identified and are thought to be inactivating. RS1 encodes a 224 amino acid protein, retinoschisin, which contains a discoidin domain but is of unknown function. We have generated a polyclonal antibody against a peptide from a unique region within retinoschisin, which detects a protein of approximately 28 kDa in retinal samples reduced with dithiothreitol, but multimers sized >40 kDa under non-reducing conditions. A screen of human tissues with this antibody reveals retinoschisin to be retina specific and the antibody detects a protein of similar size in bovine and murine retinae. We investigated the expression pattern in the retina of both RS1 mRNA (using in situ hybridization with riboprobes) and retinoschisin (using immunohistochemistry). The antisense riboprobe detected RS1 mRNA only in the photoreceptor layer but the protein product of the gene was present both in the photoreceptors and within the inner portions of the retina. Furthermore, differentiated retinoblastoma cells (Weri-Rb1 cells) were found to express RS1 mRNA and to release retinoschisin. These results suggest that retinoschisin is released by photo-receptors and has functions within the inner retinal layers. Thus, X-linked retinoschisis is caused by abnormalities in a putative secreted photoreceptor protein and is the first example of a secreted photo-receptor protein associated with a retinal dystrophy.

Blomstrand osteochondrodysplasia: three novel cases and histological evidence for heterogeneity

Blomstrand osteochondrodysplasia (BOCD) is a rare, autosomal recessive, lethal skeletal dysplasia characterized by generalized osteosclerosis and advanced skeletal maturation. The histopathological characteristics of three novel cases (two isolated cases and a sib-pair) of BOCD are presented and correlated with the clinical and radiographical findings, and the relevant literature is reviewed. The results of our study confirm the existence of two separate types of BOCD, which we propose naming type I: the severe, 'classical' form, and type II: a less severe form.

Immediate hormonal therapy compared with observation after radical prostatectomy and pelvic lymphadenectomy in men with node-positive prostate cancer

BACKGROUND

Because the optimal timing of the institution of antiandrogen therapy for prostate cancer is controversial, we compared immediate and delayed treatment in patients who had minimal residual disease after radical prostatectomy.

METHODS

Ninety-eight men who underwent radical prostatectomy and pelvic lymphadenectomy and who were found to have nodal metastases were randomly assigned to receive immediate antiandrogen therapy, with either goserelin, a synthetic agonist of gonadotropin-releasing hormone, or bilateral orchiectomy, or to be followed until disease progression. The patients were assessed quarterly during the first year and then semiannually.

RESULTS

After a median of 7.1 years of follow-up, 7 of 47 men who received immediate antiandrogen treatment had died, as compared with 18 of 51 men in the observation group (P=0.02). The cause of death was prostate cancer in 3 men in the immediate-treatment group and in 16 men in the observation group (P<0.01). At the time of the last follow-up, 36 men in the immediate-treatment group (77 percent) and 9 men in the observation group (18 percent) were alive and had no evidence of recurrent disease, including undetectable serum prostate-specific antigen levels (P<0.001). In the observation group, the disease recurred in 42 men; 13 of the 36 who were treated had a complete response to local treatment or hormonal therapy (or both), 16 died of prostate cancer, and 1 died of another disease. The remaining men in this group were alive with progressive disease at the time of the last follow-up or had had a recent relapse. Except for the treatment group (immediate therapy or observation), no clinical or histologic characteristic significantly influenced the outcome.

CONCLUSIONS

Immediate antiandrogen therapy after radical prostatectomy and pelvic lymphadenectomy improves survival and reduces the risk of recurrence in patients with node-positive prostate cancer.

Hydrocortisone with or without mitoxantrone in men with hormone-refractory prostate cancer: results of the cancer and leukemia group B 9182 study

PURPOSE

Approximately 40,000 men die each year of hormone-refractory prostate cancer (HRPC). The results of treatment with chemotherapy have been disappointing to date, with no trials demonstrating a benefit with respect to survival duration. Corticosteroids and mitoxantrone each have been shown to be active agents in this disease. The purpose of this study was to demonstrate an advantage of mitoxantrone and hydrocortisone (M+H) over hydrocortisone alone with respect to survival duration.

PATIENTS AND METHODS

Two hundred forty-two patients with HRPC were randomized to receive either M+H or hydrocortisone alone. Patients were monitored for survival, time to disease progression, time to treatment failure, response, and quality-of-life (QOL) parameters.

RESULTS

Treatment in both arms was well tolerated. Although there was a delay in time to treatment failure and disease progression in favor of M+H over hydrocortisone alone, there was no difference in overall survival (12.3 months for M+H v 12.6 months for hydrocortisone alone). There was an indication that QOL was better with M+H, in particular with respect to pain control.

CONCLUSION

M+H generated more frequent responses and a delay in both time to treatment failure and disease progression compared with hydrocortisone alone. In addition, there was a possible benefit of M+H with respect to pain control over hydrocortisone alone. No improvement in survival was observed. Although M+H could be viewed as a palliative option for patients with HRPC, new drugs and novel strategies are needed to improve survival for this disease.

Identification of SCML2, a second human gene homologous to the Drosophila sex comb on midleg (Scm): A new gene cluster on Xp22

We have identified a novel gene with homologies to the Drosophila Sex comb on midleg (Scm) gene from the short arm of the X chromosome. Scm is a member of the Polycomb group (PcG) genes, which encode transcriptional repressors essential for appropriate development in the fly and in mammals. The newly identified transcript named SCML2 (sex comb on midleg like-2, HGMW-approved symbol) is ubiquitously expressed and encodes a protein of 700 amino acids. SCML2 maps very close to the recently identified SCML1, revealing the presence of a new gene cluster in Xp22. The homology and map location identify SCML2 as a candidate gene for Xp22-linked developmental disorders, including the oral-facial-digital type I (OFDI) syndrome. A study of the SCML1-SCML2 cluster in primates indicates that the two genes are localized to the same region in Old World monkeys, New World monkeys, and prosimians, suggesting that the duplication event leading to the formation of the SCML cluster on Xp22 occurred before primate divergence.

Exclusion of RAI2 as the causative gene for Nance-Horan syndrome

Nance-Horan syndrome (NHS) is an X-linked condition characterised by congenital cataracts, microphthalmia and/or microcornea, unusual dental morphology, dysmorphic facial features, and developmental delay in some cases. Recent linkage studies have mapped the NHS disease gene to a 3.5-cM interval on Xp22.2 between DXS1053 and DXS443. We previously identified a human homologue of a mouse retinoic-acid-induced gene (RAI2) within the NHS critical flanking interval and have tested the gene as a candidate for Nance-Horan syndrome in nine NHS-affected families. Direct sequencing of the RAI2 gene and predicted promoter region has revealed no mutations in the families screened; RAI2 is therefore unlikely to be associated with NHS.

Identification and characterization of the human homologue (RAI2) of a mouse retinoic acid-induced gene in Xp22

We have identified a novel human gene during studies of a 1.3-Mb region of Xp22 between DXS418 and DXS999. A PAC contig spanning the region was constructed, sequenced, and analyzed by gene and exon prediction programs and by homology searches. Further investigation of predicted exons from PAC clone 389A20 led to the identification of a single-exon gene, designated RAI2 (retinoic acid-induced 2). RAI2 mapped 28 kb centromeric to marker DXS7996, between DXS7996 and DXS7997, and was transcribed from centromere to telomere. Northern blot analysis and reverse transcription-polymerase chain reaction analysis revealed expression of a 2.5-kb transcript in four fetal tissues (brain, lung, kidney, and heart) and eight adult tissues (heart, brain, placenta, lung, skeletal muscle, kidney, pancreas, and retina) but not in fetal or adult liver. The 530-amino-acid protein (57 kDa predicted mass) displays 94% homology with a mouse retinoic acid-induced gene product and contains a novel proline-rich (39%) domain of 68 amino acids. Retinoic acid is involved in vertebrate anteroposterior axis formation and cellular differentiation and has been shown to modulate gene expression controlling early embryonal development, suggesting a developmental role for RAI2. RAI2 remains a candidate gene for diseases mapping to the Xp22 region.

Localisation of X linked recessive idiopathic hypoparathyroidism to a 1.5 Mb region on Xq26-q27

X linked recessive idiopathic hypoparathyroidism (HPT) has been observed in two kindreds from Missouri, USA. Affected subjects, who are males, suffer from infantile onset of epilepsy and hypocalcaemia, which appears to be the result of an isolated congenital defect of parathyroid gland development; females are not affected and are normocalcaemic. The gene causing HPT has been previously mapped to a 7 cM interval, flanked centromerically by F9 and telomerically by DXS98, in Xq26-q27, and an analysis of mitochondrial DNA has established a common ancestry for these two kindreds. In order to define further the map location of HPT and thereby facilitate its isolation, we have undertaken linkage studies using polymorphic loci whose order has been established as Xcen - DXS1001 - DXS294 - DXS102 - F9 - DXS1232 - DXS984 - CDR1 - DXS105 - DXS1205 - DXS1227 - DXS98 - DXS52 - Xqter, within this region. Our results established linkage (lod score > 3) between HPT and eight of these 12 loci and indicated that the most likely location of HPT was within a 1.5 Mb interval flanked centromerically by F9 and telomerically by DXS984. Thus, the results of this study have helped to refine the map location of HPT, and this will facilitate the identification of this putative developmental gene and its role in the embryological formation of the parathyroids.

Mutational analysis of PHEX gene in X-linked hypophosphatemia

Hypophosphatemic rickets is commonly an X-linked dominant disorder (XLH or HYP) associated with a renal tubular defect in phosphate transport and bone deformities. The XLH gene, referred to as PHEX, or formerly as PEX (phosphate regulating gene with homologies to endopeptidases on the X-chromosome), encodes a 749-amino acid protein that putatively consists of an intracellular, transmembrane, and extracellular domain. PHEX mutations have been observed in XLH patients, and we have undertaken studies to characterize such mutations in 46 unrelated XLH kindreds and 22 unrelated patients with nonfamilial XLH by single stranded conformational polymorphism and DNA sequence analysis. We identified 31 mutations (7 nonsense, 6 deletions, 2 deletional insertions, 1 duplication, 2 insertions, 4 splice site, 8 missense, and 1 within the 5' untranslated region), of which 30 were scattered throughout the putative extracellular domain, together with 6 polymorphisms that had heterozygosity frequencies ranging from less than 1% to 43%. Single stranded conformational polymorphism was found to detect more than 60% of these mutations. Over 20% of the mutations were observed in nonfamilial XLH patients, who represented de novo occurrences of PHEX mutations. The unique point mutation (a-->g) of the 5'untranslated region together with the other mutations indicates that the dominant XLH phenotype is unlikely to be explained by haplo-insufficiency or a dominant negative effect.

Identification and characterization of a novel serine-threonine kinase gene from the Xp22 region

Eukaryotic protein kinases are part of a large and expanding family of proteins. Through our transcriptional mapping effort in the Xp22 region, we have isolated and sequenced the full-length transcript of STK9, a novel cDNA highly homologous to serine-threonine kinases. A number of human genetic disorders have been mapped to the region where STK9 has been localized including Nance-Horan (NH) syndrome, oral-facial-digital syndrome type 1 (OFD1), and a novel locus for nonsyndromic sensorineural deafness (DFN6). To evaluate the possible involvement of STK9 in any of the above-mentioned disorders, a 2416-bp full-length cDNA was assembled. The entire genomic structure of the gene, which is composed of 20 coding exons, was determined. Northern analysis revealed a transcript larger than 9.5 kb in several tissues including brain, lung, and kidney. The mouse homologue (Stk9) was identified and mapped in the mouse in the region syntenic to human Xp. This location is compatible with the location of the Xcat mutant, which shows congenital cataracts very similar to those observed in NH patients. Sequence homologies, expression pattern, and mapping information in both human and mouse make STK9 a candidate gene for the above-mentioned disorders.

5-Fluorouracil and leucovorin therapy in patients with hormone refractory prostate cancer: an Eastern Cooperative Oncology Group phase II study (E1889)

This report is a multi-institutional phase II study designed to obtain the response rate, survival, and toxicity profile for patients having hormone-refractory prostate cancer. Patients who had bidimensionally measurable prostate carcinoma in first or second remission after previous hormonal therapy but no history of chemotherapy were eligible. Patients were treated with leucovorin, 20 mg/m2 intravenously, followed by 5-fluorouracil (5-FU), 425 mg/m2 intravenously daily for 5 days, with cycles repeated every 28 days. Of 38 eligible patients, 3 (7.9%) had partial responses to therapy and 20 (52.6%) had stable disease. Median survival was 11.6 months for all 38 patients and median time to progression was 4.4 months. Most of the serious side effects were gastrointestinal or hematologic and overall, 23 of 38 patients (60.5%) experienced at least one grade 3 or 4 treatment-related toxicity of any type, as measured by the National Cancer Institute common toxicity criteria. Five patients (13.2%) withdrew from the study because of adverse reactions from chemotherapy. We conclude that treatment of hormone-refractory prostate cancer patients with 5-FU and leucovorin chemotherapy produced few responses at the cost of significant side effects. Further investigation of this combination is not warranted in this setting.

Characterization of SCML1, a new gene in Xp22, with homology to developmental polycomb genes

Using exon trapping, we have identified a new human gene in Xp22 encoding a 3-kb mRNA. Expression of this RNA is detectable in a range of tissues but is most pronounced in skeletal muscle and heart. The gene, designated "sex comb on midleg-like-1" (SCML1), maps 14 kb centromeric of marker DXS418, between DXS418 and DXS7994, and is transcribed from telomere to centromere. SCML1 spans 18 kb of genomic DNA, consists of six exons, and has a 624-bp open reading frame. The predicted 27-kDa SCML1 protein contains two domains that each have a high homology to two Drosophila transcriptional repressors of the polycomb group (PcG) genes and their homologues in mouse and human. PcG genes are known to be involved in the regulation of homeotic genes, and the mammalian homologues of the PcG genes repress the expression of Hox genes. SCML1 appears to be a new human member of this gene group and may play an important role in the control of embryonal development.

High-resolution physical map of the X-linked retinoschisis interval in Xp22

X-linked retinoschisis (RS) is the leading cause of macular degeneration in young males and has been mapped to Xp22 between DXS418 and DXS999. To facilitate identification of the RS gene, we have constructed a yeast artificial chromosome (YAC) contig across this region comprising 28 YACs and 32 sequence-tagged sites including seven novel end clone markers. To establish the definitive marker order, a PAC contig containing 50 clones was also constructed, and all clones were fingerprinted. The marker order is: Xpter-DXS1317-(AFM205yd12-DXS7175-DXS7992) -60N8-T7-DXS1195-DXS7993-DXS7174 -60N8-SP6-DXS418-DXS7994-DXS7995-DXS7996-+ ++HYAT2-25HA10R-HYAT1-DXS7997-DXS7998- DXS257-434E8R-3542R-DXS6762-DXS7999-DXS 6763-434E8L-DXS8000-DXS6760-DXS7176- DXS8001-DXS999-3176R-PHKA2-Xcen. A long-range restriction map was constructed, and the RS region is estimated to be 1300 kb, containing three putative CpG islands. An unstable region was identified between DXS6763 and 434E8L. These data will facilitate positional cloning of RS and other disease genes in Xp22.

Linkage studies of a Missouri kindred with autosomal dominant spondyloepimetaphyseal dysplasia (SEMD) indicate genetic heterogeneity

A four-generation kindred (14 affected and 10 unaffected members) from Missouri, U.S.A. in which spondyloepimetaphyseal dysplasia (SEMD) had been inherited as an autosomal dominant disorder was investigated for linkage to 13 candidate loci: COL2AI, COL9AI, COL9A2, COL9A3, COL10A1, COL11A1, COL11A2, PSACH, FGFR3, decorin, CRTL1, COMP, and PTHRP. Mutations of COL2A1, COL9A2, COL10, and FGFR3 have been reported previously in the Strudwick type of SEMD, multiple epiphyseal dysplasia type 2 (EDM2), the Schmid type of metaphyseal dysplasia, and in achondroplasia, respectively, and the pseudoachondroplasia (PSACH) locus has been mapped to chromosome 19p12. In addition, mutations in COL9 and COL11A are associated with murine forms of degenerative joint disease and chondroplasia, respectively. The family proved informative for 12 of the 13 loci and was uninformative at the decorin locus. Linkage between this form of SEMD, designated the Missouri variant, SEMDMO, and the 12 informative candidate loci was excluded (LOD scores < -2.00 at theta = 0.005 to 0.15), thereby indicating further genetic heterogeneity in these inherited disorders of bone and cartilage development.