SUMMARY The Luteinizing hormone/chorionic gonadotropin receptor (LHR) plays a critical role in human male sexual development. Both gain-of-function and loss-of-function mutations of the LHR have been described. Gain-of-function mutations are dominant and cause constitutive activation of the receptor resulting in familial male-limited precocious puberty (FMPP). All activating mutations are single point mutations and are located in the transmembrane domain (TM). TM helix Ⅵ harbors the largest number of activating mutations with the codon of Asp-578 being the hot-spot of mutation. Besides causing abnormal sexual development, constitutively activated LHR may predispose an individual to the development of testicular neoplasia. The anti-thesis of FMPP is Leydig cell hypoplasia (LCH). This is caused by mutations that inactivate the LHR resulting in subnormal male sexual development or male pseudohermaphroditism. Inactivating mutations are recessive. The genetic cause of LCH is variable and there is no mutation hot-spot. Genotype-phenotype correlation can be identified in LCH with the milder form caused by mutated LHR with residual activity and the severe form caused by absence of signal transduction activity of the mutated receptor. Molecular diagnosis of the disorders caused by mutation of the LHR can be achieved by direct sequencing of the LHR gene.

SUMMARY Constitutional full trisomy 21 is a common disorder in which abnormal spermatogenesis has been previously described. However, constitutional mosaic trisomy 21 in an otherwise normal but infertile male has not been explored. We report a case with low level mosaic trisomy 21 in a non-syndrome but azoospermic patient. We also propose that the patient's azoospermia may be related to the constitutional mosaic trisomy 21 and thus resulting in a late onset of testicular failure.

Objective: Prader-Willi syndrome (PWS) is characterized by severe hypotonia and feeding difficulties in early infancy, followed by excessive eating and gradual development of morbid obesity in later infancy or early childhood. Patients with PWS are often too young to manifest sufficient features or have atypical findings, making genetic testing important to confirm the diagnosis of PWS. Approximately 99% of patients with PWS have a diagnostic abnormality in the parent-specific methylation imprint within the Prader-Willi critical region (PWCR) at chromosome 15q11.2-q12. Of them, 70% have a paternal deletion; 25% have a maternal uniparental disomy (UPD); and <5% have a mutation in the imprinting center. Methods: Current techniques can identify a diagnostic abnormality, such as paternal deletion or maternal UPD for most of patients with PWS, but they are labor-intensive and cost-expensive. Multiplex ligation-dependent probe amplification (MLPA) is a novel, simple, and cost-effective technique for analysis of relative quantification in a single assay, which has recently been applied for the detection of genomic deletions, duplications, and amplifications in a variety of genes. Results: Six out of 20 patients referred for genetic diagnosis of PWS were found to have a deletion by MLPA, confirmed by FISH and DNA methylation analysis with 100% concordance. Conclusion: MLPA's high sensitivity and specificity for deletion detection is the same as FISH or Southern blot based analysis. Additional collaborative effort for developing and validating the complete MLPA-PWS assay, for not only detecting deletion but also identifying methylation abnormality, is on going.

Objective: Spinal muscular atrophy(SMA), an autosomal recessive neuromuscular degeneration of the anterior horn cells of the spinal cord and brain stem, results in one of the most common diseases with muscle fatigue and atrophy. Most SMA cases including all the types are due to the homozygous deletion of at least exon 7 within the survival motor neuron 1 (SMN-1) gene. Although a "golden standard" assay (PCR with mismatch primer followed by enzyme digestion) is very reliable for the identification of homozygous SMN-1 deletion, the carrier detection of heterozygous SMN-1 deletion remains a challenge. Methods: Some PCR-based gene dosage assays or multiplex PCR allow for the determination of the copy number of SMN-1 gene to identify heterozygous deletion, but these procedures are often time consuming and available on a limited clinical basis. Recently developed MLPA (multiplex ligation-dependent probe amplification) is an efficient procedure that can accurately analyze relative quantification to establish the copy number of the SMN gene. We performed a validation for simultaneous detection of homozygous SMN-1 deletions of SMA patients and heterozygous SMN-1 deletions of SMA carriers in a simple assay using a MLPA-SMA assay specific reagent. Results: Six out of 20 patients with SMA were found to have homozygous SMN-1 deletion, confirmed by the PCR/digestion assay. All 4 parents of the children with SMA had heterozygous SMN-1 deletion, confirmed by an independent relative quantitative analysis. Conclusion: MLPA provides a simple, rapid and accurate method of simultaneously detecting homozygous deletions and heterozygous deletions in a single assay for both SMN-1 and SMN-2 genes.

Objective: To develop a molecular screening test for genetic defects on hearing loss related genes has significant impacts on early identification of hereditary hearing loss and genetic susceptibility to aminoglycoside ototoxicity. Early identification of pre-lingual hearing loss is very important for patient's language development, academic achievement, and social skill. Two common mutations, the 235delC in GJB2 gene and the mutation A1555G in mitochondrial DNA, are included in the newly developed screening panel for Chinese population. Methods: A molecular genetic assay, based on fluorescent labeled multiplex PCR and automatic DNA fragment analyzing techniques, was developed to detect both mutations simultaneously. Results: This assay was able to detect both mutations from patient's samples, and pooled DNA tests, as well as suitable to detect mutation from the DNA extracted from dried blood spot and buccal swab. Conclusion: This assay could be a useful tool for newborn screening and carrier screening for the hereditary hearing loss for the Chinese population.

SUMMARY Infantile (INCL, NCL1) and late-infantile (LINCL, NCL2) neuronal ceroid lipofuscinoses have been found to result from genetic deficiency of genes CLN1 and CLN2, respectively. The application of molecular analyses can facilitate prenatal diagnosis for families affected by NCL1 or NCL2, in which the familial mutation(s) have been identified. Molecular testing with allele-specific primer extension and DNA sequencing was performed in nine pregnancies, four from two NCL1 families and five from five NCL2 families. Lysosomal enzyme activity assays were carried out as well.Four fetuses from three pregnancies in NCL1 families were found to be carriers for a mutation 451C-T in the CLN1 gene and one was normal. Prenatal testing of three NCL2 families who carried mutation R208X in the CLN2 gene showed that all fetuses were carriers. In NCL2 families who carried either mutation IVS5-1C or/and IVS5-1A two normal pregnancies were detected. Our studies indicate that DNA testing, which may provide definitive prenatal diagnosis for NCL, may be used in combination with lysosomal enzyme activity analyses.

SUMMARY Fluorescence in situ hybridization (FISH) has become an important diagnostic tool as an adjunct to classical cytogenetics. FISH utilizes DNA probes comprised of specific nucleic acid sequences tagged with fluorescent molecules to identify the number and location of specific DNA sequences in human cells. These probes can be used to determine various numerical and structural chromosomal aberrations, in many cases, gene dosage and/or structure alterations. Chromosomal abnormalities are responsible for a considerable number of birth defects, and more than 50% of spontaneous abortions. These numbers have been significantly higher since the advent of FISH technology that allows the detection of submicroscopic chromosome alterations. The clinic application of FISH technology in postnatal, prenatal, and preimplantation diagnoses has been playing an important role in the diagnosis and prevention of birth defects. As new technologies evolve, more and more new FISH techniques - such as subtelomeric FISH, multicolor FISH (M-FISH), comparative genomic hybridization (CGH), and microarray - are used in clinical diagnoses, the role of FISH technology in both research and clinical aspects of birth defects will surely continue to expand.

SUMMARY Therapy-related acute myeloid leukemia (tAML) is one of the two forms of secondary acute myeloid leukemia, with one derived from de novo myelodysplastic syndrome (MDS) and the other from exposure to environmental or therapeutic agents such as radiation and toxins. There has been a marked increase in the number of incidences of therapy-related acute myeloid leukemia. It has become a distinctive disease because of its etiology and genetic tumorigenesis. The majority of tAML resulting from the use of cytotoxic agents can be divided into two groups based on the drugs administered to the patient. The first group includes the use of alkylating agents, and the second group includes agents that bind to the enzyme DNA-topoisomerase Ⅱ. Due to the unfavorable outcome of the disease and the need for prompt intensive treatment, a timely accurate diagnosis of tAML is critical to patient care. Cytogenetic study can detect abnormalities most commonly associated with tAML and thus providing important diagnostic information. However, utilizing cytogenetic analysis alone cannot guarantee prompt and accurate results. In this study, an interesting case with therapy-related myelodysplastic syndrome and acute myeloid leukemia (tMDS/tAML) will be presented. A laboratory diagnostic strategy for tAML laboratory diagnosis will also be proposed.

SUMMARY　Nephropathic cystinosis is a lethal inborn error of metabolism that destroys kidney function by age 10 years. It is characterized by lysosomal cystine accumulation. How the cystine causes the phenotype is an open question. We propose that during apoptosis, permeablized lysosomes permit cystine to reach the cytosol where mixed disulfide formation occurs, augmenting apoptosis by interaction with a variety of pro-apoptotic proteins.

Objective:To purify a kind of deoxyribonuclease from earthworm Eisenia foetida (named earthworm DNase, EDNase) and study its characteristics. Methods: Acetone precipitation, ion-exchange chromatography, high performance liquid chromatography, SDS-PAGE, CapiUary electrophoresis isoelectric focusing and MALDI-TOP MS were used for the study. Results: This purified protocol improved 137-fold purification and 45.6 % recovery of enzyme activity. The molecular mass of EDNase was estimated to be 63 000. Mg2+ , Mn2+ and Ca2+ were strong inhibitors of EDNase, while Na+ slightly increasd the enzyme activity. The enzyme was completely stable in the pH range from 4. 4 to 5.2 and had a pH optimum of 4.8. The optimum temperature was 37℃ and the enzyme was stable up to 40 ℃. The pI of the enzyme was 6. 20. Km and Vmax for the enzyme were 1.52 g/L and 4. 89 mg/(mL ·min), respectively, with calf thymus DNA as substrate. The enzyme was able to degrade chromosemal DNA, linear λbacteriophage DNA as well as supereoiled plasmid DNA, but didn' t display any RNase activity. Conclusion: This kind of deoxyribonuclease possesses unique characteristics, which is different from the deoxyribonucleases which we have known before.